WAEC 2020 · Paper 1 · Q25

Calculate, correct to two decimal places, the area enclosed by the line $3x - 5y + 4 = 0$ and the axes.

Worked solution (try it first)

Where the line meets the $x$ -axis, $y = 0$ : $3x + 4 = 0$ , so $x = -\frac{4}{3}$ .
Where it meets the $y$ -axis, $x = 0$ : $-5y + 4 = 0$ , so $y = \frac{4}{5}$ .
The region is a right-angled triangle with legs $\frac{4}{3}$ and $\frac{4}{5}$ : area $= \frac{1}{2} \times \frac{4}{3} \times \frac{4}{5}$
$= \frac{8}{15}$ .
$\frac{8}{15} = 0.533$ , which is 0.53 square units, option C.