Question

A person covers a distance in 24 minutes if he runs at an average speed of 27 km/h. Find his average speed per hour to reduce the time of journey to 18 minutes?

Answer 1

$$\begin{gathered} \mathrm{Distance}=\mathrm{Speed}\times \mathrm{Time}=27\times \frac{24}{60} \\ =27\times \frac{2}{5}=\frac{54}{5}=10.8\mathrm{Km}. \\ \mathrm{New}\mathrm{time}=18\mathrm{minutes}=\frac{18}{60}\mathrm{hours}=\frac{3}{10}\mathrm{hours} \\ \mathrm{Average}\mathrm{Speed}=\frac{\mathrm{Distance}}{\mathrm{Time}}=\frac{10.8}{{\displaystyle \frac{3}{10}}}=\frac{108}{3}=36\mathrm{Km}/\mathrm{h}. \\ \mathrm{His}\mathrm{average}\mathrm{speed}\mathrm{is}36\mathrm{km}/\mathrm{h}\mathrm{to}\mathrm{reduce}\mathrm{the}\mathrm{time}\mathrm{of}\mathrm{journey}\mathrm{to}18\mathrm{minutes}. \end{gathered}$$