A car covers 30 km is 30 minutes and the next 30 km is 40 minutes. Calculate the average speed for the entire journey.

$\begin{array}{c}\\ \text{30 min}\text{= }\frac{\text{30}}{\text{60}}\text{hr = }\frac{1}{2}\text{ hr}\end{array}$

$\text{40 min}\text{= }\frac{40}{60}\text{hr =}\frac{2}{3}\text{ hr}$

$\text{total time}\text{= }\frac{1}{2}\text{+}\frac{2}{3}\text{= 7/6 hr}$

$\text{total distance= 30 km+ 30 km= 60 km}$

$\text{average speed= }\frac{\frac{60}{7}}{6}\text{= 60×}\frac{6}{7}\text{ =}\frac{360}{7}\text{ = 51}\text{.42 }\frac{\text{km}}{\text{hr}}$