Propositions and their Converses (Propositions aur unke Converses): Class 9 Maths Chapter 9 Hinglish mein
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Is chapter mein aap kya seekhenge
- Proposition ko ek aise sentence ki tarah pehchaano jo ya to true ho ya false, aur use 'if X then Y' form mein likho
- Kisi proposition ke 'if' aur 'then' parts ko swap karke uska converse banao, setting ko bina badle
- Tay karo ki proposition aur uska converse true hain ya nahi: true wale ko prove karo aur har false wale ke liye counterexample do
- Samjhao ki ek counterexample kisi claim ko galat kyun saabit kar deta hai, jabki bahut saare matching examples use prove nahi karte
- Isosceles-triangle theorem aur Baudhāyana–Pythagoras theorem ke converses prove karo
- Doosri phrasings mein bhi wahi matlab pehchaano, jaise 'X implies Y' aur 'Y when X'
NCERT Mathematics Class 9, Chapter 9, pp. 1–7 par based original companion text. Yeh NCERT se juda nahi hai aur NCERT ne ise endorse nahi kiya hai.
9.1 Propositions aur 'if … then …' form
Kuch sentences check kiye ja sakte hain aur kuch nahi. 'Kolkata Hooghly ke kinaare hai' true hai. ' ek even number hai' false hai. Lekin 'Please namak pass karo' ek request hai, 'Kya bus late hai?' ek question hai aur 'Biryani sabse achha khaana hai' ek opinion hai. In teeno mein se kisi ko bhi seedhe true ya false nahi keh sakte.
Aisa sentence jo ya to true ho ya false, lekin dono nahi.
Example' ek prime number hai' ek proposition hai. Yeh false nikalta hai, kyunki
To false sentence bhi proposition (कथन) hi ginaa jaata hai. Zaroori yeh hai ki uska ek pakka answer ho, true ya false. Maths ke bahut saare propositions do chhote statements ko if aur then words se jodte hain. Yeh raha ek, jo tumne pichhli class mein prove kiya tha.
Kisi triangle mein, agar do sides ki length same ho, to un do sides ke saamne wale angles bhi equal hote hain.
If ke baad wale part ko kaho, aur then ke baad wale part ko . Yahan hai 'do sides equal hain' aur hai 'unke saamne wale angles equal hain'. Ab dono parts ko swap karo. Tumhe ek naya proposition milta hai: kisi triangle mein, agar do angles equal hon, to un angles ke saamne wali sides ki length same hoti hai.
'If then ' ka converse proposition 'if then ' hai. Ise 'if' part aur 'then' part ko swap karke banate hain.
Example'Agar koi number 5 par khatam hota hai, to woh odd hai' ka converse hai 'agar koi number odd hai, to woh 5 par khatam hota hai'.
3/3Banana fruit hai lekin mango nahi, isliye converse false hai.
Do slots par 'If' aur 'then' likha hai. Pehle step mein orange card X, 'yeh mango hai', If slot mein hai aur green card Y, 'yeh fruit hai', then slot mein; ek panel kehta hai True: har mango ek fruit hai. Doosre step mein dono cards jagah badalte hain, to sentence banta hai 'Agar yeh fruit hai, to yeh mango hai', aur panel poochhta hai ki kya har fruit mango hai. Teesre step mein panel par ek cross, False word aur ek banana dikhta hai: banana fruit hai lekin mango nahi.
Hum aksar 'if then ' ko ' implies ' likhte hain, ya arrow se: Arrow ko 'implies' padho. Tab converse (विलोम) hai Arrow bas doosri taraf point karta hai.
Fig. 9.1 mein ek true proposition ne false converse diya. To is chapter ka bada sawaal hai: kya swap ke baad bhi truth bachta hai? Kabhi bachta hai aur kabhi nahi, jaisa agle sections dikhate hain.
Answer dekho
- (A) ek prime number hai.
- (C) Har square ki chaar equal sides hoti hain.
- (E)
Answer dekho
Answer (B) Agar koi number odd hai, to woh 5 par khatam hota hai.
Answer dekho
Answer (1) Y, (2) X
9.2 Kya true proposition ka converse bhi true hota hai?
Section 9.1 ke triangle propositions ke pair se shuru karo. Pehla ek theorem hai jo tum pehle se jaante ho. Aage padhne se pehle doosre ko khud settle karne ki koshish karo.
3/4 aur mein angle, angle aur side match karte hain.
Triangle PQR ka apex P upar hai aur Q aur R par equal angles mark kiye gaye hain; note poochhta hai ki kya PQ, PR ke equal hai. Doosre step mein P se QR par ek dashed altitude PS girti hai, aur S par right-angle marks hain. Teesre step mein dono halves, PQS aur PRS, alag-alag colours mein shaded hain aur notes matching parts batate hain: S par dono angles 90 degrees hain, PS common hai, isliye triangles congruent hain. Aakhri step mein PQ aur PR par tick marks aate hain aur note conclude karta hai PQ = PR.
Agar kisi triangle ke do angles equal hon, to un angles ke saamne wali sides equal hoti hain.
To yahan proposition aur uska converse dono true hain. Kya aisa hamesha hota hai? Ek rozmarra ka proposition try karo.
Ek city aur uska state
Proposition P: agar koi person Pune mein rehta hai, to woh person Maharashtra mein rehta hai. Iska converse Q likho. Kya P true hai? Kya Q true hai?
Pehle khud try karo. Phir solution ek-ek step karke kholo.
3/3Nagpur ka resident Y mein hai lekin X mein nahi: Q ka ek counterexample.
Ek bada blue oval Maharashtra mein rehne wale sab logon (Y) ko dikhata hai aur uske andar ek chhota orange circle Pune mein rehne wale sab logon (X) ko. Pehle step mein sirf do regions dikhte hain, X circle poori tarah Y oval ke andar hai. Doosre step mein Meera ke liye ek dot circle ke andar tick ke saath aata hai, jo Pune mein rehti hai: X mein hona use Y mein rakhta hai. Teesre step mein Nagpur ke ek resident ke liye ek diamond oval ke andar lekin circle ke bahar aata hai, ek cross aur is note ke saath ki yeh Y mein hai lekin X mein nahi: converse ka counterexample.
Nagpur ka resident Q ka ek counterexample hai. Fig. 9.3 jaisi picture mein, 'if then ' ka counterexample woh point hai jo region ke andar ho lekin region ke bahar.
Ek particular case jo proposition ke 'if' part ko true aur 'then' part ko false bana de. Ek akela counterexample saabit kar deta hai ki proposition false hai.
Example'Agar koi number odd hai, to woh prime hai' ka counterexample hai: odd hai, lekin
Prove karna aur disprove karna bilkul alag-alag level ke kaam hain. Kisi baat ko true kehne ke liye aisa argument chahiye jo har case mein chale, un cases mein bhi jo kisi ne check nahi kiye. False kehne ke liye bas ek case (प्रत्युदाहरण) kaafi hai, chahe kitne bhi doosre cases match karte rahe hon. Isiliye mathematicians counterexamples dhoondhte rehte hain.
12 aur 4 ke multiples
Yeh raha ek claim P: agar koi whole number 12 se divisible hai, to 4 bhi use divide karta hai. Samjhao ki P sahi kyun hai. Phir uska converse Q likho aur tay karo ki Q sahi hai ya nahi.
Pehle khud try karo. Phir solution ek-ek step karke kholo.
Answer dekho
Answer (D)
Answer dekho
Answer Galat
Answer dekho
Answer (B) aur
9.3 Jab dono directions true hon
Kabhi-kabhi converse har test paar kar leta hai. Ek classic case factors ginne se aata hai. Kuch numbers ke factors list karo aur gino: kin numbers ka count odd aata hai?
Perfect squares aur odd factor counts
Koi bhi positive integer lo. Claim P: agar kisi whole number ke liye ho, to ke factors ka count odd hota hai. Iska converse Q: agar ke factors ka count odd ho, to kisi whole number ke liye hota hai. Dono claims ko aur par test karo.
Pehle khud try karo. Phir solution ek-ek step karke kholo.
3/3 khud se pair banata hai, kyunki count odd hai.
Numbers ki do rows. Upar wali row mein 40 ke factors hain: 1, 2, 4, 5, 8, 10, 20, 40. Pehle step mein blue arcs 1 ko 40 se, 2 ko 20 se, 4 ko 10 se aur 5 ko 8 se jodte hain: chaar pairs, aath factors. Neeche wali row mein 36 ke factors hain: 1, 2, 3, 4, 6, 9, 12, 18, 36. Doosre step mein green arcs 1 ko 36 se, 2 ko 18 se, 3 ko 12 se aur 4 ko 9 se jodte hain, aur beech mein 6 bina arc ke reh jaata hai. Teesre step mein 6 ke charon taraf ek dashed loop banta hai aur ek note kehta hai 6 × 6 = 36, isliye 36 ke 9 factors hain.
Argument kis direction ko prove karta hai?
ko kisi bhi factor se divide karne par ek aur factor milta hai, aur dono ka product hota hai. Fig. 9.4 mein har arc aise hi ek factor pair ko jodta hai. Do alag numbers ke beech ka arc do factors cover karta hai, isliye sirf arcs hamesha even number of factors hi ginte hain.
Ab maan lo factors ka count odd hai. Arcs sab kuch cover nahi kar sakte, isliye kisi factor ka koi arc nahi hai: woh khud apna partner hai, yaani Tab ek perfect square hai. Yeh argument odd count se shuru hota hai aur square par khatam hota hai, isliye yeh Q ko prove karta hai. P ke baare mein yeh abhi kuch nahi batata.
P prove karne ke liye doosre end se shuru karo. Agar to khud se pair banata hai. Kya koi doosra number bhi khud se pair bana sakta hai? Tab Lekin agar to aur agar to Isliye : kisi number ka zyada se zyada ek hi self-paired factor hota hai.
Baaki sab factors do alag numbers ke pairs mein hote hain, jo even count dete hain. Usme ek self-paired factor jodne se total odd ho jaata hai. To P bhi true hai.
Answer dekho
Answer 9 factors
Answer dekho
Answer (C) Woh perfect square nahi ho sakta.
Answer dekho
Answer Galat
9.4 Chaar possible outcomes
Ab tak humne ek true proposition dekha jiska converse false tha, aur aise pairs jahan dono directions sahi hain. Kya aisa ho sakta hai ki proposition false ho aur uska converse true?
Equal perimeters aur congruent triangles
P: agar do triangles ke perimeters equal hon, to woh congruent hote hain. Q: agar ek triangle doosre se congruent ho, to dono ke perimeters match karte hain. Tay karo ki har ek true hai ya nahi. True wale ko justify karo aur false wale ke liye counterexample do.
Pehle khud try karo. Phir solution ek-ek step karke kholo.
3/3B, A par fit nahi hota, isliye P false hai.
Pehle step mein ek blue right-angled triangle A dikhta hai jiski sides 6, 8 aur 10 cm hain, uske perimeter 6 + 8 + 10 = 24 cm ke saath. Doosre step mein uske paas ek orange equilateral triangle B aata hai jiski sides 8 cm hain, uska perimeter bhi 24 cm hai. Teesre step mein triangle B ki ek dashed copy triangle A ke upar slide hoti hai: outlines match nahi karti, aur note kehta hai 'Same perimeter, not congruent' (perimeter same, lekin congruent nahi).
Examples ko saath-saath rakho, to har combination dikh jaata hai (Table 9.2).
| Example | |
|---|---|
| Dono true | perfect square factors ka count odd (Example 3) |
| Sirf proposition true | 12 ka multiple 4 ka multiple (Example 2) |
| Sirf converse true | equal perimeters congruent triangles (Example 4) |
| Dono false | prime odd (2 ek even prime hai; 9 odd hai lekin prime nahi) |
Seekh yeh hai: proposition true hai ya nahi, yeh jaanne se uske converse ke baare mein kuch pata nahi chalta. Har ek ko alag se check karna padta hai, proof se ya counterexample se. Neeche wala checker tumhe kuch number propositions aur unke converses ko 1 se 100 tak ke numbers par test karne deta hai.
Left mein koi item tap karo, phir right mein uska match.
Answer dekho
- 8 ka multiple even : sirf proposition
- teen equal sides teen equal angles : dono
- even 4 ka multiple : sirf converse
- prime odd : koi nahi
Answer dekho
Answer (C) Woh congruent ho bhi sakte hain aur nahi bhi.
9.5 Baudhāyana–Pythagoras theorem aur uska converse
Tumne Baudhāyana–Pythagoras theorem kai baar use kiya hai, jaise Part 1 ke Chapter 1 mein points ke beech distances nikaalne ke liye. Yeh raha use dhyaan se state karne ka ek tareeka.
Sides , aur wale triangle mein: agar sides aur ke beech ka angle right angle ho, to
Theorem ka converse likhna
Upar state kiye gaye Baudhāyana–Pythagoras theorem ka converse likho.
Pehle khud try karo. Phir solution ek-ek step karke kholo.
Converse sahi likhna sirf aadha kaam hai: use abhi prove bhi karna hai. Neeche wala proof khud theorem ko use karta hai, ek doosre triangle par jo hum banate hain.
4/4Teeno sides same, isliye
Left mein triangle PQR apni sabse lambi side PQ = c par tika hai, QR = a, PR = b, aur upar ke vertex R par question mark hai; upar ka label kehta hai a squared plus b squared barabar c squared. Doosre step mein right mein ek right triangle DEF aata hai, jiska right angle F par hai, EF = a aur DF = b. Teesre step mein uski teesri side DE par c likha jaata hai, kyunki DE squared barabar a squared plus b squared hai, jo c squared ke barabar hai. Aakhri step mein R par question mark ki jagah right-angle mark aa jaata hai: triangles SSS se congruent hain, isliye angle R barabar angle F, yaani 90 degrees.
Agar kisi triangle ki sides is relation ko satisfy karti hain: to side ke saamne wala angle right angle hota hai.
Dhyaan do ki proof original theorem ko sirf is triangle par use karta hai: jo right-angled hai kyunki humne use aise hi banaya. Yeh ke baare mein kuch bhi assume nahi karta, isliye argument gol-gol nahi ghoom raha.
Kya koi right angle hai?
In triangles mein se kis mein right angle hai, aur kahan? (a) Sides 20 cm, 21 cm aur 29 cm. (b) Sides 7 cm, 8 cm aur 11 cm.
Pehle khud try karo. Phir solution ek-ek step karke kholo.
Answer dekho
Answer (B) Ismein 41 cm wali side ke saamne right angle hai.
- Isliye ke saamne wala angle hai
- Legs aur wala ek right triangle banao
- Theorem se, uski teesri side hai
- Dono triangles congruent hain (SSS)
Answer dekho
- Legs aur wala ek right triangle banao
- Theorem se, uski teesri side hai
- Dono triangles congruent hain (SSS)
- Isliye ke saamne wala angle hai
Answer dekho
Answer Galat
9.6 'If X then Y' kehne ke doosre tareeke
Rozmarra ki English mein ek hi 'if … then …' idea ko kehne ke kai tareeke hain. Table 9.3 ka har sentence bilkul wahi baat kehta hai jo agar koi number 10 ka multiple hai, to woh even hai.
| Pattern | Example |
|---|---|
| Agar , to (if … then). | Agar koi number 10 ka multiple hai, to woh even hai. |
| implies (). | 10 ka multiple hona even hona imply karta hai. |
| jab (when). | Koi number even hota hai jab woh 10 ka multiple ho. |
| jab bhi (whenever). | Koi number even hota hai jab bhi woh 10 ka multiple ho. |
| Har , hai (every). | 10 ka har multiple even hai. |
| tabhi jab (only if). | Koi number 10 ka multiple tabhi hota hai jab woh even ho. |
4/4Koi number 10 ka multiple tabhi hota hai jab woh even ho. Phir bhi
Do tiles, orange X tile jis par 'a multiple of 10' likha hai aur green Y tile jis par 'even' likha hai, baari-baari chaar sentence patterns mein rakhi jaati hain. Step 1: 'If X, then Y'. Step 2: tiles khisak kar 'Y when X' banati hain. Step 3: 'Every X is Y'. Step 4: 'X only if Y'. Har pattern ke neeche wahi line X implies Y dikhati hai, yaani tiles sentence mein idhar-udhar jaane par bhi matlab kabhi nahi badalta.
Aakhri pattern mein bahut log uljh jaate hain. ' only if ' (yaani tabhi jab) ka matlab yeh nahi hai: Yeh kehta hai ki kabhi bhi ke bina nahi hota, yaani To converse banane se pehle sentence ko 'if … then …' form mein dobara likho, aur pehchaano, aur sirf tab unhe swap karo.
Answer dekho
Answer (B) public holiday hai
Answer dekho
Answer (C) 4 ka har multiple even hai.
Answer dekho
Answer Galat
Summary aur key points
- Proposition aisa sentence hai jo ya to true ho ya false (Section 9.1).
- 'If then ' ka converse 'if then ' hai. 'Sides , , wale triangle mein' jaisa scene set karne wala phrase nahi badalta (Example 5).
- ' implies ', '', ' when ' aur 'every is ', sabka matlab 'if then ' hai (Section 9.6).
- Counterexample 'if' part ko true aur 'then' part ko false banata hai. Proposition ko false dikhane ke liye ek hi kaafi hai (Section 9.2).
- Bahut saare matching cases proof nahi bante: Fermat ke numbers paanch baar prime the aur phir fail ho gaye (Fermat ki kahani).
- Proposition aur uska converse dono true ho sakte hain, dono false ho sakte hain, ya ek true aur ek false (Table 9.2).
- Koi number perfect square hai if and only if uske factors ka count odd hai. Har direction ke liye apna argument chahiye (Section 9.3).
- Triangle mein equal angles ke saamne equal sides hoti hain, aur hone par ke saamne right angle banna hi hai: dono converses true hain (isosceles converse, Baudhāyana–Pythagoras converse).
Exercise Set 9.1
Practice questions answers ke saath (NCERT “Exercise Set 9.1”)
Questions 1 se 12 mein har ek ek proposition deta hai. Kuch 'if … then …' form mein nahi likhe gaye: pehle unhe dobara likho (Section 9.6 dekho). Converse likho, phir tay karo ki dono mein se kaun se statements true hain. Har true statement ke saath reason do aur har false ke saath counterexample. Questions 18 se 22 extra practice ke liye hain.
Agar ek transversal do parallel lines ko kaatta hai, to alternate interior angles equal hote hain.
Solution dikhao
AnswerConverse: agar ek transversal do lines ko kaatta hai aur equal alternate interior angles banata hai, to lines parallel hain.
Converse: agar ek transversal do lines ko kaatta hai aur alternate interior angles equal hain, to dono lines parallel hain.
Proposition: true. Parallel lines ke liye corresponding angles equal hote hain, aur har alternate interior angle ek corresponding angle ke barabar hota hai, kyunki vertically opposite angles equal hote hain.
Converse: true. Agar alternate interior angles equal hain, to wahi vertically-opposite-angle wala step corresponding angles ke ek pair ko equal bana deta hai, aur jo lines transversal ke saath equal corresponding angles banati hain woh parallel hoti hain.
Agar koi triangle equilateral hai, to woh isosceles hai (uski kam se kam do sides equal hain).
Solution dikhao
AnswerConverse: agar koi triangle isosceles hai, to woh equilateral hai.
Converse: agar koi triangle isosceles hai (uski kam se kam do sides equal hain), to woh equilateral hai.
Proposition: true. Equilateral triangle ki teeno sides equal hoti hain, to unmein se do to pakka equal hain.
Converse: false. 5 cm, 5 cm aur 8 cm sides wale triangle ki do sides equal hain lekin woh equilateral nahi hai.
Ek triangle hai jismein , se altitude hai (yaani ) aur , se altitude hai (yaani ). Proposition: agar , to .
Fig. 9.9 aur is triangle ki altitudes hain: Ek triangle ABC jiska A upar hai aur B aur C neeche left aur right mein. B se ek dashed line side AC ko E par right angle par milti hai, aur C se ek dashed line side AB ko F par right angle par milti hai. Right-angle marks dono feet dikhate hain.
Solution dikhao
AnswerConverse: agar , to .
Converse: altitudes aur wale mein, agar , to .
ka area do tareekon se likho: base ke saath height hai, aur base ke saath height hai.
Proposition: true. Agar , to dono sides ko is common length se divide karo, milega.
Converse: true. Agar , to dono sides ko is common length se divide karo, milega.
Converse ke liye ek aur raasta: right triangles aur ka hypotenuse common hai aur hai, isliye woh RHS se congruent hain. Tab aur equal angles ke saamne equal sides hoti hain.
Kisi bhi numbers , aur ke liye: agar , to .
Solution dikhao
AnswerConverse: agar , to .
Converse: agar , to .
Proposition: true. Equal numbers ko same number se multiply karne par results equal aate hain.
Converse: false. , , lo: tab lekin .
Jab ho, tab converse sahi hai: dono sides ko se divide karo. Isiliye equation solve karte waqt tum dono sides ko sirf aise number se divide kar sakte ho jo zero na ho.
Positive integers aur ke liye: jab bhi dono perfect cubes hon, unka product bhi perfect cube hota hai.
Solution dikhao
AnswerConverse: agar perfect cube hai, to aur dono perfect cubes hain.
'If … then …' form mein: agar aur perfect cubes hain, to perfect cube hai. Converse: agar perfect cube hai, to aur dono perfect cubes hain.
Proposition: true. Agar aur , to
Converse: false. aur lo: cube hai, lekin na cube hai na .
Real numbers aur ke liye: agar , to .
Solution dikhao
AnswerConverse: agar , to .
Converse: agar , to .
Proposition: true. Equal numbers ki fourth powers equal hoti hain.
Converse: false. aur lo: lekin .
Real numbers aur ke liye: agar , to .
Solution dikhao
AnswerConverse: agar , to .
Converse: agar , to .
Proposition: true. Equal numbers ki fifth powers equal hoti hain.
Converse: true. Maan lo hai lekin , jaise . Agar to ko khud se paanch baar multiply karne par milta hai.
Agar to negative hai aur nahi, isliye . Agar , to isliye jiska matlab hai .
Har case deta hai, jo ke against hai. Isliye .
Yahan se Question 12 tak ek positive integer hai. 18 ka har multiple 3 se aur 6 se bhi divisible hai.
Solution dikhao
AnswerConverse: agar 3 aur 6 dono se divisible hai, to 18 se divisible hai.
'If … then …' form mein: agar 18 se divisible hai, to woh 3 aur 6 dono se divisible hai. Converse: agar 3 aur 6 dono se divisible hai, to 18 se divisible hai.
Proposition: true.
Converse: false. , 3 se aur 6 se divisible hai lekin 18 se nahi. ( bhi chalega.)
Jab bhi 45 se divisible ho, woh 5 se aur 9 se divisible hota hai.
Solution dikhao
AnswerConverse: agar 5 aur 9 dono se divisible hai, to 45 se divisible hai.
'If … then …' form mein: agar 45, ko divide karta hai, to 5 aur 9 dono ko divide karte hain. Converse: agar 5 aur 9 dono se divisible hai, to 45 se divisible hai.
Proposition: true.
Converse: true. 9 se divisible hone ka matlab hai ki ke prime factorisation mein hai. 5 se divisible hone ka matlab hai ki usmein hai, jo ek alag prime hai. Isliye usmein yeh sab hai: aur , ko divide karta hai.
Jab bhi kisi prime ke liye ho, ke theek chaar factors hote hain.
Solution dikhao
AnswerConverse: agar ke theek 4 factors hain, to kisi prime number ka cube hai.
'If … then …' form mein: agar kisi prime ke liye , to ke theek chaar factors hain. Converse: agar ke theek 4 factors hain, to kisi prime ka cube hai.
Proposition: true. Agar aur prime hai, to uska ek hi prime factor hai, isliye uske factors , , aur hain: theek 4.
Converse: false. ke theek 4 factors () hain lekin woh cube nahi hai.
form ka har number, jahan , aur teen alag primes hain, theek aath factors rakhta hai.
Solution dikhao
AnswerConverse: agar ke theek 8 factors hain, to teen alag primes ka product hai.
'If … then …' form mein: agar teen alag primes ke liye , to ke theek aath factors hain. Converse: agar ke theek 8 factors hain, to teen alag primes ka product hai.
Proposition: true. Agar , to har factor , , mein se kuch ka product hai: Yeh 8 factors hain.
Converse: false. ke theek 8 factors () hain, lekin woh teen alag primes ka product nahi hai.
Jab aur ka ek hi common factor 1 ho, to number odd hota hai.
Solution dikhao
AnswerConverse: agar odd hai, to aur ka 1 ke alawa koi common factor nahi hai.
'If … then …' form mein: agar aur ka ek hi common factor 1 hai, to odd hai. Converse: agar odd hai, to aur ka 1 ke alawa koi common factor nahi hai.
Proposition: true. Agar even hota, to aur dono even hote, aur unka common factor 2 hota. Isliye odd hi hona chahiye.
Converse: true. aur ka common factor unke difference ko bhi divide karta hai. Isliye ya to hai ya . Kyunki odd hai, , isliye .
Har claim kehta hai ki ek formula hamesha prime number deta hai. Har claim ko ek counterexample se todo.
Har whole number ke liye prime hai.
Solution dikhao
Answer lene par milta hai
se , , milte hain, sab prime, lekin lene par milta hai
Har whole number ke liye prime hai.
Solution dikhao
Answer lene par milta hai
se tak ki saari values prime hain, jisse claim safe lagta hai. Lekin lene par milta hai
Har whole number ke liye prime hai.
Solution dikhao
Answer lene par milta hai
se , , , milte hain, sab prime, lekin lene par milta hai
Har statement ka ek counterexample dhoondho.
Kisi prime ko double karke 1 jodne par hamesha prime milta hai.
Solution dikhao
Answer se milta hai.
se , , milte hain, sab prime. Lekin lene par aata hai jo prime nahi hai.
Har odd number ke liye prime hai.
Solution dikhao
Answer se milta hai.
se aur se milta hai, dono prime. Lekin lene par aata hai jo prime nahi hai.
Yeh raha ek true statement: 12 se divisible har number 2 aur 6 dono se divisible hota hai.
Samjhao ki yeh statement true kyun hai.
Solution dikhao
12 ka multiple hai isliye woh 2 se aur 6 se divisible hai.
Ravi kehta hai: 'Jo number 2 aur 6 ke tests paas kar le, woh 12 se divisible hoga hi.' Kya Ravi sahi hai? Samjhao.
Solution dikhao
Nahi. Yeh test converse par tika hai, agar koi number 2 aur 6 se divisible hai, to woh 12 se divisible hai, jo false hai: 2 se aur 6 se divisible hai lekin 12 se nahi. Asal mein 6 ka har multiple pehle se even hota hai, isliye 2 check karne se kuch naya nahi milta.
Kaun se do chhote divisibility tests milkar 12 ke liye sach mein kaam karte hain?
Solution dikhao
Answer3 se aur 4 se divisibility.
3 aur 4 use karo. 4 se divisible number ke prime factorisation mein hota hai, aur 3 se divisible mein . Saath milkar unmein aata hai Yeh isliye kaam karta hai kyunki 3 aur 4 ka 1 ke alawa koi common factor nahi hai.
9 ka ek shortcut: koi number 9 se divisible theek tab hota hai jab uske digits ka sum 9 ka multiple ho. Is relationship ko do 'if … then …' sentences mein likho, batao ki har ek true hai ya nahi, aur unhe par check karo.
Solution dikhao
AnswerDono sentences true hain; number 9 se divisible hai if and only if uske digits ka sum 9 ka multiple hai.
Agar koi number 9 se divisible hai, to uske digits ka sum 9 ka multiple hai. Iska converse: agar kisi number ke digits ka sum 9 ka multiple hai, to woh number 9 se divisible hai.
Dono true hain, kyunki , aur aise hi aage. Isliye kisi number aur uske digit sum mein hamesha 9 ke multiple ka fark hota hai: ek 9 ka multiple theek tab hai jab doosra ho.
Dono saath mein: koi number 9 se divisible hai if and only if uske digits ka sum 9 ka multiple hai. Check: jo 9 ka multiple hai, aur sach mein
Uttarayan ke liye Ahmedabad ki ek kite-maker do bamboo sticks ko saath baandhti hai aur unke chaaron ends ke around ek string ghumaati hai. Sticks quadrilateral ke diagonals ban jaati hain aur string uski sides. Maan lo 'type K' quadrilaterals ki koi class hai jo woh banana chahti hai.
Fig. 9.10Sticks ko right angles par cross karna: off-centre (ek kite) aur dono ke beech mein (ek rhombus). Do frames saath-saath. Har ek mein do bamboo sticks right angles par cross karti hain aur ek dashed string unke chaaron ends ko jodti hai. Left mein sticks chhoti stick ke beech mein lekin lambi stick ke beech se kaafi upar cross karti hain, jisse kite shape banti hai. Right mein sticks dono ke beech mein cross karti hain, jisse rhombus banta hai.
Maan lo agar koi quadrilateral type K ka hai, to uske diagonals perpendicular hain. Kya use sticks right angles par hi baandhni padengi?
Solution dikhao
Haan. Har type-K quadrilateral ke diagonals perpendicular hote hain. Agar sticks kisi aur angle par cross karti hain, to frame type K ka ho hi nahi sakta.
Isi property ke saath, kya unhe right angles par baandhna type K pakka karne ke liye kaafi hai?
Solution dikhao
Nahi. Property batati hai ki har type-K shape mein kya hota hai, yeh nahi ki perpendicular diagonals wali har shape type K ki hai; woh iska converse hota, jo humein diya hi nahi gaya. Jaise, agar type K ka matlab 'rhombus' hota, to sticks ko right angles par off-centre cross karne se kite banti hai, rhombus nahi (Fig. 9.10).
Ab iske bajaay maan lo: agar kisi quadrilateral ke diagonals perpendicular hain, to woh type K ka hai. Kya ab sticks ko right angles par baandhna kaafi hai?
Solution dikhao
Haan. Perpendicular diagonals wala koi bhi quadrilateral type K ka hai, chahe sticks ki lengths kuch bhi hon aur woh kahin bhi cross karein.
(c) wali property ke saath, kya sticks ka right angles par hona zaroori hai?
Solution dikhao
Zaroori nahi. Yeh property perpendicular diagonals ke liye type K ki guarantee deti hai, lekin doosri shapes ke baare mein kuch nahi kehti. Ho sakta hai kuch type-K quadrilaterals ke diagonals perpendicular na hon.
Agar Ravi 90 se zyada score karta hai, to use A grade milta hai ka converse kaun sa sentence hai?
Answer dekho
Answer (C) Agar Ravi ko A grade milta hai, to woh 90 se zyada score karta hai.
Converse dono parts ko swap karta hai aur kuch nahi badalta. Pehla option bina swap kiye dono parts mein 'not' jodta hai, aur doosra swap karke 'not' jodta hai; dono alag statements hain.Agar koi proposition false hai, to uska converse bhi false hi hoga.
Answer dekho
Answer Galat
Example 4: 'equal perimeters congruent' false hai, lekin uska converse 'congruent equal perimeters' true hai.Aisa akela case jo proposition ke 'if' part ko true aur 'then' part ko false bana de, kehlata hai.
Answer dekho
Answer counterexample
Proposition ko false dikhane ke liye ek counterexample kaafi hai.Part 1 mein tumne yeh fact dekha tha ki semicircle mein bana angle right angle hota hai. Ise ek point aur diameter wale circle ke baare mein 'if … then …' proposition ki tarah likho. Phir iska converse likho aur tay karo ki converse true hai ya nahi.
Solution dikhao
AnswerConverse: agar to diameter wale circle par hai. Yeh true hai.
Proposition: agar diameter wale circle par koi point hai ( aur ke alawa), to
Converse: agar to diameter wale circle par hai.
Converse true hai. Right triangle mein circumcentre hypotenuse ka midpoint hota hai (Part 1, Chapter 5), isliye , aur se guzarne wala circle bilkul diameter wala circle hi hai. Isliye us par hai.
Rectangles ke baare mein aisa proposition do jo false ho aur jiska converse bhi false ho. Har verdict ko counterexample se support karo.
Solution dikhao
Answer'Same perimeter same area' false hai, aur iska converse bhi.
Proposition: agar do rectangles ka perimeter same hai, to unka area same hai. False: 2 cm by 8 cm rectangle aur 4 cm by 6 cm rectangle dono ka perimeter 20 cm hai, lekin unke areas 16 cm² aur 24 cm² hain.
Converse: agar do rectangles ka area same hai, to unka perimeter same hai. False: 2 cm by 8 cm rectangle aur 4 cm by 4 cm square dono ka area 16 cm² hai, lekin unke perimeters 20 cm aur 16 cm hain.
Apna NCERT exercise question dhoondo
Hamare practice questions ncert.ai ke liye likhe gaye hain aur NCERT exercises ko follow karte hain. Apni textbook ke question se match karne wala question dhoondo; uska answer uske saath hai.
| Tumhari NCERT textbook mein | Yahan practice question |
|---|---|
| NCERT Exercise Set 9.1, Q1 | Practice Q1 |
| NCERT Exercise Set 9.1, Q2 | Practice Q2 |
| NCERT Exercise Set 9.1, Q3 | Practice Q3 |
| NCERT Exercise Set 9.1, Q4 | Practice Q4 |
| NCERT Exercise Set 9.1, Q5 | Practice Q5 |
| NCERT Exercise Set 9.1, Q6 | Practice Q6 |
| NCERT Exercise Set 9.1, Q7 | Practice Q7 |
| NCERT Exercise Set 9.1, Q8 | Practice Q8 |
| NCERT Exercise Set 9.1, Q9 | Practice Q9 |
| NCERT Exercise Set 9.1, Q10 | Practice Q10 |
| NCERT Exercise Set 9.1, Q11 | Practice Q11 |
| NCERT Exercise Set 9.1, Q12 | Practice Q12 |
| NCERT Exercise Set 9.1, Q13 | Practice Q13 |
| NCERT Exercise Set 9.1, Q14 | Practice Q14 |
| NCERT Exercise Set 9.1, Q15 | Practice Q15 |
| NCERT Exercise Set 9.1, Q16 | Practice Q16 |
| NCERT Exercise Set 9.1, Q17 | Practice Q17 |
Quick check: MCQs
- 9.1 Propositions aur 'if … then …' form3 questions
- 9.2 Kya true proposition ka converse bhi true hota hai?3 questions
- Argument kis direction ko prove karta hai?3 questions
- 9.4 Chaar possible outcomes2 questions
- 9.5 Baudhāyana–Pythagoras theorem aur uska converse3 questions
- 9.6 'If X then Y' kehne ke doosre tareeke3 questions
Key terms (English + Hindi)
- congruentसर्वांगसमsarvaangsam
- Do figures congruent hoti hain jab ek ko doosri par exactly rakha ja sake: unki shape aur size same hoti hai.Chapter mein pehli baar yahan aaya →
- converseविलोमvilom
- Woh proposition jo 'if' part aur 'then' part ko swap karne se milta hai: 'if then ' ka converse 'if then ' hai.Chapter mein pehli baar yahan aaya →
- counterexampleप्रत्युदाहरणpratyudaharan
- Ek particular case jo proposition ke 'if' part ko true aur 'then' part ko false bana de. Proposition ko false dikhane ke liye ek counterexample kaafi hai.Chapter mein pehli baar yahan aaya →
- factor pair
- Do whole numbers jinka product diya gaya number ho, jaise ke liye aur . Pair mein ek number do baar bhi aa sakta hai, jaise mein.Chapter mein pehli baar yahan aaya →
- if and only ifयदि और केवल यदिyadi aur keval yadi
- ' if and only if ', jise likhte hain, kehta hai ki proposition aur uska converse dono true hain.Chapter mein pehli baar yahan aaya →
- implies
- ' implies ', jise likhte hain, ka matlab wahi hai jo 'if then ' ka: jab bhi true ho, bhi true hota hai.Chapter mein pehli baar yahan aaya →
- perfect squareपूर्ण वर्गpoorn varg
- Aisa whole number jo kisi whole number ko khud se multiply karne par mile, jaise Chapter mein pehli baar yahan aaya →
- propositionकथनkathan
- Aisa sentence jo ya to true ho ya false, lekin dono nahi. ', ka multiple hai' jaisa false sentence bhi proposition hi hai.Chapter mein pehli baar yahan aaya →