IGCSEMathsCambridge (CIE)International MathsCoreRevision NotesNumberIntroduction to FractionsFractions of Amounts

Fractions of Amounts (Cambridge (CIE) IGCSE International Maths)

Revision Note

Author

Naomi C

Expertise

Maths

Fractions of Amounts

How do I find a fraction of an amount?

Method 1
Divide by the denominator and multiply by the numerator
- To find $\frac{1}{3}$ of $90$ , divide it by 3
  - $90 \div 3 = 30$
- To find $\frac{2}{5}$ of $60$ , divide it by 5 then multiply it by 2
  - $60 \div 5 = 12$ , then $12 \times 2 = 24$
Method 2
Change the fraction into a decimal, then multiply
- To find $\frac{1}{4}$ of $16$ , turn $\frac{1}{4}$ into $0.25$ then multiply
  - $0.25 \times 16 = 4$
- To find $\frac{9}{10}$ of $15$ , turn $\frac{9}{10}$ into $0.9$ then multiply
  - $0.9 \times 15 = 13.5$
Method 3
Write both numbers as fractions and multiply two fractions together
- To find $\frac{2}{3}$ of $60$ , write $60$ as $\frac{60}{1}$
  - work out $\frac{2}{3} \times \frac{60}{1} = \frac{120}{3} = 40$
- To find $\frac{5}{6}$ of $\frac{8}{3}$
  - work out $\frac{5}{6} \times \frac{8}{3} = \frac{40}{18} = \frac{20}{9}$

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Author: Naomi C

Naomi graduated from Durham University in 2007 with a Masters degree in Civil Engineering. She has taught Mathematics in the UK, Malaysia and Switzerland covering GCSE, IGCSE, A-Level and IB. She particularly enjoys applying Mathematics to real life and endeavours to bring creativity to the content she creates.