Question

A car moves with a speed of 30 km per hour for half an hour 25 kilometre per hour for 1 hour and 40 kilometre per hour for 2 hours calculate average speed of a car

Answer 1

Dear Student,

$$\begin{gathered} \mathrm{distance}=\mathrm{speed}\times \mathrm{time} \\ {\mathrm{d}}_1=30\times \frac{1}{2}=15\mathrm{km} \\ {\mathrm{d}}_2=25\times 1=25\mathrm{km} \\ {\mathrm{d}}_3=40\times 2=80\mathrm{km} \\ \mathrm{Average}\mathrm{speed}=\frac{\mathrm{total}\mathrm{distance}}{\mathrm{total}\mathrm{time}} \\ \mathrm{Average}\mathrm{speed}=\frac{15+25+80}{\left({\displaystyle \frac{1}{2}}+1+2\right)} \\ \mathrm{Average}\mathrm{speed}=\frac{120}{{\displaystyle \frac{1+2+1}{2}}} \\ \mathrm{Average}\mathrm{speed}=\frac{120\times 2}{4}=60\mathrm{km}/\mathrm{h} \end{gathered}$$
Regards