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Chapter 8 · Fractions in Disguise

NCERT Class 8 · Ganita Prakash

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CHAPTER 8 OF 14

Fractions in Disguise 🍕

One half, 0.5, 50% and 2/4 are the same number wearing four different costumes. Recognising the costume is most of the work.

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Part 1 · Three Forms

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Part 2 · Decimals

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Part 3 · Comparing

1

The same number, three forms 🎭

Move freely between fraction, decimal and percentage and most questions become easy.

🎭 Learn the row, not the cell

FractionDecimalPercent
1/20.550%
1/40.2525%
3/40.7575%
1/50.220%
1/80.12512.5%
1/30.333…33⅓%
2/50.440%
3/80.37537.5%
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Fraction → decimal: divide the top by the bottom. Decimal → percent: multiply by 100. Percent → fraction: put it over 100 and reduce.

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Game 1 — Match the Forms

2

Terminating or repeating? 🔁

Every rational number, written as a decimal, either stops or repeats for ever. There is a simple test for which.

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The test: reduce the fraction, then look at the denominator’s prime factors. If they are only 2s and 5s, the decimal terminates. Any other prime and it repeats. So 3/8 (8 = 2×2×2) stops at 0.375, but 1/3 and 1/6 repeat for ever.

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A repeating decimal is still rational. 0.333… = 1/3 exactly. Being infinite does not make it irrational — only numbers like √2 and π, which never repeat and never stop, are irrational.

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Game 2 — Stops or Repeats?

3

Comparing and ordering 📊

To compare fractions, make the denominators the same — or turn them all into decimals.

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Which is bigger, 3/5 or 5/8? Common denominator 40: 3/5 = 24/40 and 5/8 = 25/40, so 5/8 wins. As decimals, 0.6 against 0.625 — same answer, sometimes faster.

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A bigger denominator does not mean a bigger fraction. 1/3 is larger than 1/8, even though 8 > 3, because the whole is cut into fewer pieces.

Game 3 — Which Is Bigger?

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Topic Mock Test

12 questions on fractions, decimals and comparing values. 🍀

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Chapter 7 · Proportional Reasoning ⚖️

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Chapter 9 · Pythagoras Theorem 📐