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Chapter 2 · Power Play

NCERT Class 8 · Ganita Prakash

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CHAPTER 2 OF 14

Power Play ⚡

Writing 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 is tiring. Writing 2¹⁰ is not. Exponents are shorthand — and they come with a small set of laws that do all the work.

Part 1 · Powers

📜

Part 2 · The Laws

🔭

Part 3 · Standard Form

1

What a power means ⚡

In an, the base a is what you multiply, and the exponent n is how many times.

⚡ Powers of 2 and 3

n2ⁿ3ⁿ
123
249
3827
41681
532243
664729
10102459049
⚠️

Two traps. First, 2³ is 8, not 6 — you multiply, not add. Second, anything to the power 0 is 1: 5⁰ = 1, 100⁰ = 1, even (−7)⁰ = 1.

⌨️

Game 1 — Work Out the Power

2

The laws of exponents 📜

Five laws cover almost every question. Learn what each one does to the exponents.

📜 The five laws

LawRuleExample
Multiply — add the powersaᵐ × aⁿ = am+n2³ × 2⁴ = 2⁷ = 128
Divide — subtractaᵐ ÷ aⁿ = am−n3⁵ ÷ 3² = 3³ = 27
Power of a power — multiply(aᵐ)ⁿ = amn(2²)³ = 2⁶ = 64
Zero powera⁰ = 19⁰ = 1
Negative power — flip ita⁻ⁿ = 1 / aⁿ2⁻³ = 1/8
💡

The laws only work with the same base. 2³ × 2⁴ = 2⁷ ✅, but 2³ × 3⁴ cannot be combined — work each out separately: 8 × 81 = 648.

✍️

Game 2 — Which Law?

3

Standard form 🔭

Very large and very small numbers are written as a × 10n, where a is between 1 and 10.

🔭 Ordinary ↔ standard form

OrdinaryStandard form
5 90,0005.9 × 10⁵
3 20,00,0003.2 × 10⁷
0.000 077 × 10⁻⁵
0.000 000 252.5 × 10⁻⁷
🎯

Which way does the sign go? A big number gets a positive power; a number smaller than 1 gets a negative power. Count how many places the decimal point moves — that is the power.

🔄

Game 3 — Into Standard Form

📝

Topic Mock Test

12 questions on exponents and standard form. Apply one law at a time. 🍀

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Chapter 1 · A Square and A Cube 🔲

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Chapter 3 · A Story of Numbers 🔢