Square Root Kya Hai? | Class 8 Maths Book 1 Ch 1

📘 Class 8 · Ganita Prakash Book 1Ch 1 · A Square and a CubePost 4 / 8⏱ 25–30 min
Square Root Kya Hai? 🌱

✅ Pehle Yeh Aata Hai?

Yeh post shuru karne se pehle, in teen sawaalon ko 1 minute mein khud try kijiye:

  1. 12² = ?
  2. 36 ke prime factors?
  3. Kya 50 perfect square?
Answers dekho
  1. 144
  2. 2 × 2 × 3 × 3
  3. Nahi (7² = 49, 8² = 64)

Teeno sahi? Badhiya, aage chaliye! Koi galat hua? Koi baat nahi, Post 2 — Square Numbers Ki Properties aur prime factorisation ek baar dekh lijiye.

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🎬 Kahani: Kisan Ka Square Khet

Kisan Ramesh ji ke paas 1156 sq m ka ek square khet hai. Unhe charon taraf baad lagaani hai, to side jaanni hai. 🌾

Unka beta bola: “Area = side × side. To woh number dhoondho jo khud se guna hoke 1156 de!” Par kaise? 30 × 30 = 900, 40 × 40 = 1600… Kya andaaze se hi chalana padega? Nahi! Aaj ek pakka tareeka seekhenge.

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📖 Concept: Square Ka Ulta: Square Root

💡 Is post ki ek badi baat: Square root ulta kaam hai: √y = x jab x² = y. Prime factorisation mein square ke har prime ki jodi hoti hai; har jodi se ek-ek prime uthao, guna karo, root mil gaya. Jodi adhoori? To number perfect square nahi.

Step 1: Square root ka matlab

4² = 16, to 4 ko 16 ka square root kehte hain: √16 = 4.

Do root: (−4)² bhi 16! To 16 ke do integer root: +4 aur −4. Symbol √ hamesha positive wala deta: √16 = 4.

Step 2: Ghatao tareeka (Post 3 se)

81 − 1 − 3 − 5 − 7 − 9 − 11 − 13 − 15 − 17 = 0 → 9 kadam → √81 = 9.

WHY? Pehle n odd ka jod n², to kadam = n. Chhote numbers ke liye badhiya.

Step 3: Prime factorisation: jodi banao

324 = 2 × 2 × 3 × 3 × 3 × 3 = (2 × 2) × (3 × 3) × (3 × 3).

Har jodi se ek: 2 × 3 × 3 = 18. To √324 = 18.

WHY? Agar y = x × x, to x ke primes y mein do baar aate. Primes ko do barabar dher mein baanto; ek dher = x.

Step 4: Square nahi to?

156 = 2 × 2 × 3 × 13. Jodi: (2 × 2), par 3 aur 13 akele → perfect square nahi.

Square banane ka jugaad: akelon ko jodi do: 156 × 3 × 13 = 156 × 39 = 6084 = 78².

Step 5: Kisan ka khet

1156 = 2 × 2 × 17 × 17 → √1156 = 2 × 17 = 34 m. Baad = 4 × 34 = 136 m.

Check: 34² = 900 + 2 × 30 × 4 + 16 = 1156 ✅

🪜 Atak Gaye? Aise Socho

  • Pehle aakhri digit test: 2, 3, 7, 8 pe khatam to root integer nahi.
  • Number ko chhote primes se baar-baar bhaag do: 2, 3, 5, 7…
  • Primes ko jodi mein ghero.
  • Har jodi se ek prime, sab guna.
  • Akela bacha? Perfect square nahi.

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🔐 Deep Concept: Kya 2800 Square Hai? Aur Har Prime Ki Power Even

2800 = 2 × 2 × 2 × 2 × 5 × 5 × 7 = 2⁴ × 5² × 7. 7 akela (power 1, odd) → square nahi.

Gehri baat: number perfect square tabhi jab har prime ki power even ho. Kyunki square karne pe har power double hoti: (2² × 3)² = 2⁴ × 3². Yahi niyam Post 1 ke “odd factors” aur Post 2 ke “zero jodi mein” ke peeche bhi hai (10 = 2 × 5, zero bhi jodi mein!).

Sabse chhota guna: 2800 ko square banane ke liye × 7 → 19600 = 140². Bhaag se bhi: 2800 ÷ 7 = 400 = 20².

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✏️ Solved Examples

Example 1 (Easy): √196 prime factorisation se.

196 = 2 × 2 × 7 × 7 → 2 × 7 = 14.

Check: 14 × 14 = 196 ✅

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Example 2 (Medium): Kya 1156 aur 2800 perfect square? (NCERT)

1156 = 2² × 17² → haan, 34. 2800 = 2⁴ × 5² × 7 → nahi.

Check: 52² = 2704, 53² = 2809, 2800 beech mein ✅

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Example 3 (NCERT style): 180 ko kis sabse chhote number se guna karein ki square bane?

180 = 2² × 3² × 5 → × 5 = 900 = 30².

Check: 30 × 30 = 900 ✅

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Ramesh ji ka khet: side 34 m, baad 136 m. Andaaza nahi, pakka hisaab! 🌾

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🏠 Square Root Kahan Kaam Aata

  • 🌾 Khet/plot ki side: area se side nikaalna.
  • 🖼️ Square photo frame: 400 sq cm ka frame = 20 cm side.
  • 🏫 Assembly: 625 bachche square mein: 25 × 25.
  • 📐 Pythagoras (aage): tirchhi doori nikaalne mein root.
  • 🧩 Puzzle tiles: 144 tukde = 12 × 12 ka square puzzle.

Area pata, side chahiye? Square root lo.

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🧭 Kab Use Karein, Kab Nahi

SituationKya kareinKyun
Chhota number (≤ 100)✅ Squares ki list ya ghataoTez
Bada number✅ Prime factorisationPakka aur saaf
Number 2, 3, 7, 8 pe khatam❌ Integer root nahiSquare nahi
Prime akela bache❌ Perfect square nahiJodi adhoori
Square banana ho✅ Akelon se guna/bhaagSab jodi poori

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❌→✅ Worked Mistake

Sawaal: √(2 × 2 × 3 × 3) = ?

❌ Galat: “Sab primes ka guna 36, phir aadha: 18.”

✅ Sahi: har jodi se ek: 2 × 3 = 6. Check: 6² = 36 ✅ (18² = 324)

🧠 Rule of thumb: Root = jodi se ek-ek prime ka guna, aadha karna nahi.

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📝 10 MCQs

Q1. √225 = ?

(a) 15
(b) 25
(c) 112.5
(d) 5
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: 15 × 15 = 225 ✅
  • (b) galat: 25 × 25 = 625, galat, isliye yeh galat.
  • (c) galat: Aadha karna root nahi hota.
  • (d) galat: 5² = 25, 225 nahi, isliye yeh galat.

Q2. 36 ke integer square roots?

(a) 6 aur −6
(b) Sirf 6
(c) 18
(d) 6 aur 18
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: Dono ka square 36 ✅
  • (b) galat: −6 bhi square karke 36 deta.
  • (c) galat: 18 aadha hai, root nahi.
  • (d) galat: 18² = 324, galat, isliye yeh galat.

Q3. √144 prime se: 144 = 2⁴ × 3²

(a) 12
(b) 24
(c) 6
(d) 72
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: 2 × 2 × 3 = 12 ✅
  • (b) galat: 24 mein ek 2 zyada liya.
  • (c) galat: 6 mein ek 2 kam liya, isliye yeh galat.
  • (d) galat: 72 to 144 ka aadha hai.

Q4. Kaunsa perfect square?

(a) 2⁴ × 3²
(b) 2³ × 3²
(c) 2 × 3²
(d) 2² × 3
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: Sab powers even ✅
  • (b) galat: 2³ ki power odd hai, isliye yeh galat.
  • (c) galat: 2 akela hai, odd power.
  • (d) galat: 3 akela hai, odd power.

Q5. 72 ko square banane ke liye kis se guna?

(a) 2
(b) 3
(c) 6
(d) 4
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 72 = 2³ × 3² → × 2 = 144 ✅
  • (b) galat: × 3 se 216, 3 akela ho jaata.
  • (c) galat: × 6 se 432, square nahi.
  • (d) galat: × 4 se 288, 2 abhi bhi odd.

Q6. √1156 = ?

(a) 34
(b) 36
(c) 24
(d) 44
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: 2 × 17 = 34 ✅
  • (b) galat: 36² = 1296, galat, isliye yeh galat.
  • (c) galat: 24² = 576, galat, isliye yeh galat.
  • (d) galat: 44² = 1936, galat, isliye yeh galat.

Q7. Ghatao tareeke mein √49 ke kadam?

(a) 7
(b) 49
(c) 13
(d) 6
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: 49 = 7², 7 kadam ✅
  • (b) galat: 49 kadam bahut zyada hain.
  • (c) galat: 13 aakhri odd ghataaya, ginti nahi.
  • (d) galat: 6 kadam ke baad 13 bachta.

Q8. 2800 square kyun nahi?

(a) 7 akela
(b) 2 akela
(c) Zero hain
(d) Even hai
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: 7 ki power 1, odd ✅
  • (b) galat: 2⁴, power even hai, isliye yeh galat.
  • (c) galat: Zero to 2 hain, even, isliye yeh galat.
  • (d) galat: Even hona galat kaaran hai.

Q9. √ symbol deta hai?

(a) Positive root
(b) Negative root
(c) Dono
(d) Square
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: √16 = 4, positive ✅
  • (b) galat: Negative ke liye −√ likhte.
  • (c) galat: Symbol sirf ek deta hai.
  • (d) galat: Square ulta kaam hai, isliye yeh galat.

Q10. 150 ko square banane ke liye kis se bhaag?

(a) 6
(b) 5
(c) 3
(d) 2
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 150 = 2 × 3 × 5² → ÷ 6 = 25 ✅
  • (b) galat: ÷ 5 = 30, square nahi.
  • (c) galat: ÷ 3 = 50, square nahi.
  • (d) galat: ÷ 2 = 75, square nahi.

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❓ FAQs (Bachchon Ke Asli Sawaal)

1. Negative number ka square root?

Class 8 mein nahi; koi integer khud se guna hoke negative nahi deta.

2. Root aur square ka rishta?

Ulta kaam: √(n²) = n, (√y)² = y.

3. Prime factorisation kaise?

2, 3, 5, 7… se baar-baar bhaag, jab tak 1 na bache.

4. Kya √2 bhi hota?

Haan, par woh integer/fraction nahi; ≈ 1.414. Andaaza: Post 5 — Square Root Ka Andaaza.

5. √(fraction)?

√(9/16) = 3/4. Upar-neeche alag root.

6. Aage kya?

Jo perfect square nahi, unka root ka andaaza: Post 5 — Square Root Ka Andaaza.

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🏋️ Practice Zone (12 Sawaal)

Q1. Easy √64 = ?

Solution dekho

8. Check ✅

Q2. Easy √400 = ?

Solution dekho

20. Check: 2 zero → 1 zero ✅

Q3. Easy 49 ke do integer root?

Solution dekho

7, −7. Check ✅

Q4. Easy √(4/25) = ?

Solution dekho

2/5. Check ✅

Q5. Medium √576 prime factorisation se.

Solution dekho

2⁶ × 3² → 2³ × 3 = 24. Check: 24² = 576 ✅

Q6. Medium Kya 288 perfect square?

Solution dekho

2⁵ × 3² → nahi. Check ✅

Q7. Medium √1764 = ?

Solution dekho

2² × 3² × 7² → 42. Check ✅

Q8. Medium Ghatao se √36.

Solution dekho

6 kadam → 6. Check ✅

Q9. NCERT style 252 × ? = square (sabse chhota).

Solution dekho

2² × 3² × 7 → 7 (1764 = 42²). Check ✅

Q10. NCERT style 2925 ÷ ? = square.

Solution dekho

3² × 5² × 13 → 13 (225). Check ✅

Q11. NCERT style Square plot 1024 sq m: side?

Solution dekho

32 m. Check: 2¹⁰ → 2⁵ ✅

Q12. NCERT style 1296 bachche square mein: har qatar?

Solution dekho

36. Check: 2⁴ × 3⁴ → 2² × 3² ✅

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🧠 HOTS (Sochne Wale Sawaal)

Q1. Ek square ka area 4 guna: side?

Solution dekho

2 guna. Check: √4 = 2 ✅

Q2. n² ke prime factors mein har power even. Kyun?

Solution dekho

Square = powers double. Check: (2 × 3)² = 2² × 3² ✅

Q3. Sabse chhota square jo 6, 9, 15 se divide?

Solution dekho

LCM 90 = 2 × 3² × 5 → × 10 = 900. Check ✅

Q4. √(0.09) = ?

Solution dekho

0.3. Check: 0.3² = 0.09 ✅

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🏆 Olympiad Corner

Q1. √(2⁸ × 5⁴)?

Solution dekho

2⁴ × 5² = 400.

Q2. Sabse chhota n ki 12n square?

Solution dekho

3.

Q3. √(1 + 3 + 5 + … + 49)?

Solution dekho

25.

Q4. 4-digit sabse chhota square?

Solution dekho

1024.

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💗 CharuMam Motivation

Ramesh ji ne andaaze ki jagah jodi banana seekha. Mushkil sawaal ko chhote tukdon (primes) mein todo, sab aasaan! 🌟

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🟢 Master Recap

  • 💡 Chaabi: Square root ulta kaam hai: √y = x jab x² = y. Prime factorisation mein square ke har prime ki jodi hoti hai; har jodi se ek-ek prime uthao, guna karo, root mil gaya. Jodi adhoori? To number perfect square nahi.
  • √y = x jab x² = y.
  • Har square ke do root: + aur −; √ deta +.
  • Ghatao: kadam = root.
  • Prime jodi se ek-ek = root.
  • Akela prime = square nahi.
  • Square banane ke liye akelon se guna/bhaag.

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