Introducing Ratio

≈ 25 min

A ratio compares two quantities of the same kind, written with a colon, like $2:3$ . Ratios behave like fractions: multiply or divide both parts by the same number to get an equivalent ratio, and divide by the HCF to simplify. So $4:6 = 2:3$ .

Sharing in a ratio. To split R $60$ between two people in the ratio $2:3$ , first count the total parts: $2 + 3 = 5$ . One part is $60 \div 5 = 12$ . So the shares are $2 \times 12 =$ R $24$ and $3 \times 12 =$ R $36$ (and indeed $24 + 36 = 60$ ).

Simplify the ratio $4:6$ to its lowest terms.

$2:3$

$1:2$

$3:2$

$4:3$

A cooldrink mix uses concentrate and water in the ratio $1:4$ . For $3$ cups of concentrate, how many cups of water are needed?

R $60$ is shared between Ann and Ben in the ratio $2:3$ . How many rand does Ben get?

In a class the ratio of girls to boys is $3:2$ . What fraction of the class are girls?

$\dfrac{3}{2}$

$\dfrac{2}{5}$

$\dfrac{3}{5}$

$\dfrac{1}{2}$