JAMB 2003 · UME · Q10

Find $\left(\frac{1}{0.06} \div \frac{1}{0.042}\right)^{-1}$ , correct to two decimal places.

Worked solution (try it first)

Dividing by $\frac{1}{0.042}$ is the same as multiplying by 0.042: $\frac{1}{0.06} \times 0.042 = \frac{0.042}{0.06}$ .
Multiply top and bottom by 1000: $\frac{42}{60} = 0.7$ .
The power $-1$ means the reciprocal: $\frac{1}{0.7} = 1.428\ldots$ , which is 1.43 to 2 decimal places, option D.