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Rational numbers · 1 mark

As society grew more complex, measuring became just as important as counting. If a farmer divides a field of wheat among his three children, how much does each get? If a recipe calls for half a cup of ghee, how do we represent that mathematically?

Answer: Each child gets 13 of the field (if it is shared equally), and half a cup is 12 cup. Both are fractions: numbers that stand for parts of a whole.

Step-by-step solution

Idea: Whole numbers count whole things. To describe a part of one whole, we write a fraction: the denominator tells how many equal parts the whole is cut into, and the numerator tells how many parts we take.

  1. The field is one whole shared equally into 3 parts, so each child gets 1 ÷ 3 = 13 of the field.½ mark
  2. Half a cup means the cup is cut into 2 equal parts and one part is used: 12 cup. Numbers like 13 and 12 are called fractions.½ mark
Each child gets 1/3 of the field; half a cup of ghee is 1/2 cup. These are fractions.

Check: 13 + 13 + 13 = 1: the three shares make the whole field ✓.

Answer to write in the exam

Field shared equally among 3 ⇒ each gets 1 ÷ 3 = 13 of the field

Half a cup = 12 cup

∴ Parts of a whole are written as fractions: 13 and 12.

Common mistakes that cost marks

  • Writing 31 instead of 13: the number of parts (3) goes in the denominator.
  • Saying each child gets 3 parts; each gets 1 of the 3 equal parts.
  • Writing half as 0.2 instead of 0.5 or 12.

How this can come in the exam

MCQ (1 mark)

A rope is cut into 8 equal pieces and 3 pieces are used. The fraction of rope used is

  1. 83
  2. 38
  3. 58
  4. 35
Show answer

(B) 38
3 of 8 equal parts = 38.

Short answer (2 marks)

A farmer gives 14 of his field to one son and 13 to his daughter. What fraction of the field is left?

Show answerGiven away: 14 + 13 = 312 + 412 = 712 (1 mark). Left: 1 − 712 = 512 (1 mark).

Try one yourself

A pizza is shared equally by 5 friends. What fraction does each get, and what fraction do two of them get together?

Show answer

Each gets 15; two together get 25.

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