Unit Conversion Aur Ratio | Class 8 Maths Book 1 Ch 7

📘 Class 8 · Ganita Prakash Book 1Ch 7 · Proportional Reasoning-1Post 8 / 9⏱ 25–30 min
Unit Conversion Aur Ratio 📏

✅ Pehle Yeh Aata Hai?

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

  1. 1 km = ? m
  2. 1 kg = ? g
  3. Trairashika (Post 6 — Trairashika: Rule Of Three)?
Answers dekho
  1. 1000
  2. 1000
  3. Phala × ichchha ÷ pramana

Teeno sahi? Badhiya, aage chaliye! Koi galat hua? Koi baat nahi, Post 6 — Trairashika: Rule Of Three dekh lijiye.

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🎬 Kahani: Papa Ke Do Flat

Papa do flat dekh rahe. Broker A: “1200 sq ft.” Broker B: “110 sq m.” 🏢

Bhaiya: “1200 to 110 se kahin bada!” Didi: “Units alag hain, pagle.”

Usi shaam Dadi ka thermometer 101°F dikha raha tha, doctor ne poochha “Celsius mein?” Aaj dono pakka karenge, aur ek chaunkane wala sach bhi. 🌡️

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📖 Concept: Unit Badalna = Ek Fixed Ratio Se Guna

💡 Is post ki ek badi baat: Do units ke beech ek fixed ratio hota: 1 m = 100 cm matlab m : cm = 1 : 100. Isliye conversion trairashika hi hai: maatra × (nayi unit per purani unit).

Step 1: Conversion factor = 1 ka roop

(100 cm / 1 m) = 1, kyunki upar-neeche same lambai. Isse guna karne se maatra nahi badalti, sirf unit.

3.5 m × (100 cm / 1 m) = 350 cm. “m” kat gaya!

WHY trick kaam karti? 1 se guna = kuch nahi badla. Unit kaatna batata sahi factor upar hai ya neeche.

Step 2: Tareeka 2: Trairashika

1 inch = 2.54 cm. 12 inch? 12 × 2.54 = 30.48 cm. Proportion: 1 : 2.54 :: 12 : x.

Kab aasaan: ek step ka conversion.

Step 3: Area mein factor ka square

1 m = 100 cm, to 1 sq m = 100 × 100 = 10000 sq cm, 100 nahi!

WHY? Square ki lambai aur chaudai dono 100 guna → area 100 × 100 guna (Post 1 — Proportional Badlaav Kya Hai? mein dekha: lambai × k → area × k²). Volume mein k³.

Step 4: Papa ka flat

1 m ≈ 3.28 ft → 1 sq m ≈ 3.28 × 3.28 ≈ 10.76 sq ft. 110 sq m ≈ 110 × 10.76 ≈ 1184 sq ft.

To 1200 sq ft thoda bada (16 sq ft). Bhaiya ka “kahin bada” galat, par jawab sahi! Check: 1200 ÷ 10.76 ≈ 111.5 sq m > 110 ✅

Step 5: Multi-step

72 km/h → m/s: 72 × 1000/3600 = 20 m/s. Har unit ka factor ek-ek karke.

🪜 Atak Gaye? Aise Socho

  • Purani aur nayi unit likho.
  • Factor likho: “1 purani = ? nayi”.
  • Area? square; volume? cube.
  • Guna karo, unit kaato.
  • Check: chhoti unit mein bada number aaye.

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🔐 Deep Concept: Kya Har Conversion Ratio Hai? Temperature Ka Twist

Dadi ka 101°F. Agar proportion lagaayein: 100°C = 212°F, to 101°F = 101 × 100/212 ≈ 47.6°C?? Itna bukhaar to jaan le leta! 😱

Sahi: °C = (°F − 32) × 5/9 = 69 × 5/9 ≈ 38.3°C.

WHY ratio fail? 0°C = 32°F, dono ke zero alag. Proportional rishta hamesha 0 → 0 (Post 3 — Ratio Ka Simplest Form ki line (0, 0) se guzarti). Lambai mein 0 m = 0 cm, isliye ratio chalta. Temperature mein ek fixed offset 32 hai (taxi ke fixed ₹40 jaisa, Post 9 — Proportion Ke Tricky Sawaal).

Par farak proportional hai! Temperature mein 1°C badhaav = 1.8°F badhaav. 36.6°C se 38.3°C = 1.7°C ≈ 3.1°F.

Unifying idea: conversion = same factor tabhi, jab zero zero se mile. Yahi proportional ki pehchaan. 🎯

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✏️ Solved Examples

Example 1 (Easy): 2.4 km = ? m

2.4 × 1000 = 2400 m.

Check: 2400 ÷ 1000 = 2.4 ✅

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Example 2 (Medium): 3 sq m = ? sq cm

3 × 10000 = 30000 sq cm.

Check: 300 cm × 100 cm = 30000 ✅

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Example 3 (NCERT style): Kamra 4 m × 5 m. Tile 25 cm × 25 cm. Kitni tile?

Kamra 400 × 500 = 200000 sq cm, tile 625 → 320.

Check: 16 tile × 20 tile = 320 ✅

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Papa ka faisla: 1200 sq ft ≈ 111.5 sq m, broker B ke 110 se thoda bada. Aur Dadi ka 38.3°C bukhaar: dawai, aaram, aur unit pe dhyaan! 🏢🌡️

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🏠 Unit Conversion Roz Ki Zindagi Mein

  • 🏠 Property: sq ft, sq m, gaj, bigha.
  • 🌡️ Bukhaar: °F aur °C.
  • 🚗 Speed: km/h aur m/s.
  • 👖 Kapde: inch mein waist.
  • 💊 Dawai: mg aur ml.

1 gaj (sq yard) = 9 sq ft, kyunki 1 yard = 3 ft aur 3 × 3 = 9. Phir wahi square wala niyam!

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🧭 Kab Use Karein, Kab Nahi

SituationKya kareinKyun
Ek step✅ Factor se gunam → cm
Unit kaatna✅ Factor 1 ka roop100 cm/1 m
Area✅ Factor²10000
Volume✅ Factor³1 m³ = 10⁶ cm³
Temperature❌ Seedha ratio nahiOffset 32

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❌→✅ Worked Mistake

Sawaal: 5 sq m = ? sq cm

❌ Galat: 5 × 100 = 500 sq cm.

✅ Sahi: 5 × 10000 = 50000 sq cm. Check: 1 m × 5 m = 100 cm × 500 cm = 50000 ✅

🧠 Rule of thumb: Lambai factor k, to area k², volume k³. Aur ratio sirf tab, jab zero = zero.

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📝 10 MCQs

Q1. 1 sq m = ? sq cm

(a) 10000
(b) 100
(c) 1000
(d) 10
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi: 2.4 × 1000 = 2400 m ✅
  • (b) galat: 240 mein 100 se guna kiya, 1000 nahi.
  • (c) galat: 24000 mein 10000 se guna ho gaya.
  • (d) galat: 24 mein sirf 10 se guna kiya.

Q2. 110 sq m vs 1200 sq ft?

(a) 1200 sq ft thoda bada
(b) 110 bada
(c) Same
(d) 1200 kahin bada
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Sahi jawab: ≈ 1184 < 1200 ✅
  • (b) galat: Ulta hai, isliye yeh galat.
  • (c) galat: Thoda farak hai, isliye yeh galat.
  • (d) galat: Sirf thoda, isliye yeh galat.

Q3. 101°F ≈ ?

(a) 38.3°C
(b) 47.6°C
(c) 69°C
(d) 56°C
Solution dekho

Sahi jawab: (a)

  • (a) sahi: (101 − 32) × 5/9 ≈ 38.3°C ✅
  • (b) galat: 47.6 seedha ratio lagaane ki galti hai.
  • (c) galat: 69 mein sirf 32 ghataya, × 5/9 nahi kiya.
  • (d) galat: 56 kisi sahi hisaab se nahi aata.

Q4. Temperature ratio kyun nahi?

(a) Zero alag
(b) Unit nahi
(c) Hamesha ratio
(d) Bahut bada
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 0°C = 32°F, dono ke zero alag ✅
  • (b) galat: Temperature ki unit hoti hai, woh kaaran nahi.
  • (c) galat: Seedha ratio lagaane se 47.6°C jaisa galat aata.
  • (d) galat: Number ka size kaaran nahi, offset kaaran hai.

Q5. 72 km/h = ? m/s

(a) 20
(b) 72
(c) 200
(d) 7.2
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 72 × 1000 ÷ 3600 = 20 ✅
  • (b) galat: 72 to unit badle bina wahi number hai.
  • (c) galat: 200 mein 3600 se bhaag nahi kiya.
  • (d) galat: 7.2 mein sirf 10 se bhaag diya.

Q6. 1 sq yard = ? sq ft

(a) 9
(b) 3
(c) 6
(d) 27
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 3 ft × 3 ft = 9 sq ft ✅
  • (b) galat: 3 mein square lena bhool gaye.
  • (c) galat: 6 mein 3 + 3 jod diya, guna nahi.
  • (d) galat: 27 to cube (3³) hai, volume ke liye.

Q7. Conversion factor 100 cm/1 m kyun 1?

(a) Same lambai
(b) Hamesha 100
(c) Kat jaata
(d) Galat
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Upar-neeche same lambai, isliye 1 ✅
  • (b) galat: Number 100 dikhta, par maan 1 hai.
  • (c) galat: Unit katti hai, par isse factor 1 nahi banta.
  • (d) galat: Factor sahi hai, galat nahi.

Q8. 1 m³ = ? cm³

(a) 10⁶
(b) 10⁴
(c) 100
(d) 10³
Solution dekho

Sahi jawab: (a)

  • (a) sahi: 100 × 100 × 100 = 10⁶ ✅
  • (b) galat: 10⁴ to area (sq) ka factor hai.
  • (c) galat: 100 sirf lambai ka factor hai.
  • (d) galat: 10³ mein 10 ka cube liya, 100 ka nahi.

Q9. 2.4 km = ? m

(a) 2400
(b) 240
(c) 24000
(d) 24
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Bilkul sahi jawab: × 1000 ✅
  • (b) galat: × 100 kiya, isliye yeh galat.
  • (c) galat: × 10000 kiya, isliye yeh galat.
  • (d) galat: × 10 kiya, isliye yeh galat.

Q10. Temp mein 1°C badhaav = ?

(a) 1.8°F
(b) 33.8°F
(c) 1°F
(d) 32°F
Solution dekho

Sahi jawab: (a)

  • (a) sahi: Farak proportional: 1°C = 1.8°F ✅
  • (b) galat: 33.8°F to 1°C ka maan hai, badhaav nahi.
  • (c) galat: 1°F bahut kam, factor 1.8 hai.
  • (d) galat: 32 offset hai, badhaav ka factor nahi.

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❓ FAQs (Bachchon Ke Asli Sawaal)

1. sq ft se sq m?

÷ 10.76 (lagbhag).

2. 1 hectare?

10000 sq m = 100 m × 100 m.

3. Litre aur cm³?

1 litre = 1000 cm³.

4. °C se °F?

°F = °C × 9/5 + 32.

5. Mile?

1 mile ≈ 1.609 km.

6. Aage?

Tricky sawaal: Post 9 — Proportion Ke Tricky Sawaal.

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🏋️ Practice Zone (12 Sawaal)

Q1. Easy 4.5 kg = ? g

Solution dekho

4500. Check ✅

Q2. Easy 350 cm = ? m

Solution dekho

3.5. Check ✅

Q3. Easy 2 hectare = ? sq m

Solution dekho

20000. Check ✅

Q4. Easy 2.5 litre = ? ml

Solution dekho

2500. Check ✅

Q5. Medium 6 sq m = ? sq cm

Solution dekho

60000. Check ✅

Q6. Medium 36 km/h = ? m/s

Solution dekho

10. Check ✅

Q7. Medium 15 m/s = ? km/h

Solution dekho

54. Check: 54 × 5/18 = 15 ✅

Q8. Medium 10 inch = ? cm

Solution dekho

25.4. Check ✅

Q9. NCERT style 50°C = ? °F

Solution dekho

122°F. Check: (122 − 32) × 5/9 = 50 ✅

Q10. NCERT style Kamra 3 m × 4 m, tile 20 cm × 20 cm?

Solution dekho

300. Check: 15 × 20 ✅

Q11. NCERT style 2 m³ = ? litre

Solution dekho

2000. Check ✅

Q12. NCERT style Kis temp pe °C = °F?

Solution dekho

−40. Check: −40 × 9/5 + 32 = −40 ✅

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🧠 HOTS (Sochne Wale Sawaal)

Q1. Map 1 : 50000. Map pe 4 sq cm, asli?

Solution dekho

Lambai k = 50000 → area × 25 × 10⁸ → 1 sq km. Check: 2 cm = 1 km, 2 × 2 ✅

Q2. Cube 1 m ko 1 cm cube mein kaata?

Solution dekho

10⁶. Check ✅

Q3. 98.6°F = ?

Solution dekho

37°C. Check ✅

Q4. Kya km aur mile proportional?

Solution dekho

Haan, 0 = 0. Check ✅

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🏆 Olympiad Corner

Q1. 1 sq km = ? hectare

Solution dekho

100.

Q2. 90 km/h = ? m/s

Solution dekho

25.

Q3. 3 sq ft = ? sq inch

Solution dekho

432.

Q4. 0°C = ? °F

Solution dekho

32.

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💗 CharuMam Motivation

Ab broker ho ya doctor, units aapko dhokha nahi de sakti. Factor, square, aur zero ka dhyaan! 📏

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🟢 Master Recap

  • 💡 Chaabi: Do units ke beech ek fixed ratio hota: 1 m = 100 cm matlab m : cm = 1 : 100. Isliye conversion trairashika hi hai: maatra × (nayi unit per purani unit).
  • Conversion = fixed ratio se guna.
  • Factor 1 ka roop, unit kaato.
  • Area k², volume k³.
  • sq m ≈ 10.76 sq ft.
  • Temperature: offset, seedha ratio nahi.
  • Proportional: 0 → 0.

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