Fractions of amounts

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There are many methods to find fractions of amounts, including:

multiplying fractions
a

Multiplying fractions

Example

Find \(\frac{2}{5}\) of 40.

Multiply \(\frac{2}{5}\) by 40.

\(\frac{2}{5} \times 40\)

\(= \frac{2}{5} \times \frac{40}{1}\) (40 can be written as \(\frac{40}{1}\))

\(= \frac{80}{5}\)

= 16

Unitary method

A unitary method simply means finding out what one of something is worth first.

Example

Find \(\frac{3}{4}\) of 16.

First work out \(\frac{1}{4}\) of 16, then multiply the answer by 3 to get \(\frac{3}{4}\).

\(\frac{1}{4}\) of 16 is the same as \(16 \div 4\) which is 4.

If \(\frac{1}{4}\) of 16 = 4, then \(\frac{3}{4}\) of 16 must be three times this amount, so \(\frac{3}{4}\) of 16 = 12 (\(4 \times 3 = 12\)).

Question

Which is larger, \(\frac{2}{3}\) of 24 or \(\frac{3}{4}\) of 20?

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