WAEC 2022 · Paper 1 · Q12

The length of a piece of stick is $1.75\text{ m}$ . A boy measured it as $1.80\text{ m}$ . Find the percentage error.

Worked solution (try it first)

The error is $1.80 - 1.75 = 0.05$ m.
Divide by the true length and multiply by 100: $\frac{0.05}{1.75} \times 100\% = \frac{5}{1.75}\%$ .
$\frac{5}{1.75} = \frac{20}{7} = 2\frac67$ , so the percentage error is $2\frac67\%$ , option B.