Question

If a : b = 3 : 4, then find 4a : 5b. [1 Mark]

Answer 1

Given that a : b = 3 : 4

$\therefore$ $\frac{a}{b}$ = $\frac{3}{4}$ ............. (1)

(0.5 marks)

Since we need to find 4a : 5b,
Multiplying both sides of equation (1) by $\frac{4}{5}$, we have

$\frac{a}{b}$ $\times$ $\frac{4}{5}$ = $\frac{3}{4}$ $\times$ $\frac{4}{5}$

$\frac{4a}{5b}$ = $\frac{3}{5}$

Hence $4a:5b$ = $3:5$
(0.5 marks)