JAMB 1991 · UME · Q3

Find, correct to 3 decimal places, $\left(\dfrac{1}{0.05} \div \dfrac{1}{5.005}\right) - (0.05 \times 2.05)$ .

Worked solution (try it first)

$\frac{1}{0.05} = 20$ .
Dividing by $\frac{1}{5.005}$ is the same as multiplying by 5.005, so the bracket is $20 \times 5.005 = 100.1$ .
The second bracket is $0.05 \times 2.05 = 0.1025$ .
Subtract: $100.1 - 0.1025 = 99.9975$ .
The fourth decimal is 5, so round up: 99.998, option A.