The base of a triangle is increased by 40%. By what percentage (correct to two decimal places) should its height be increased so that the area increases by 60%?

$$\eqalign{ & {\text{Base}} - 40\% = \frac{2}{5} \cr & {\text{Area}} - 60\% = \frac{3}{5} \cr & {\text{Area}} \to {\text{5:8}} \cr & {\text{Base}} \to {\text{5:7}} \cr & {\text{Height}} \to \frac{5}{5}:\frac{8}{7} \cr & \underbrace {7\,\,:\,\,8}_1 \cr & \frac{1}{7} \times 100 = 14.29\% \cr} $$