A person travels from P to Q at a speed of 40 kmph and returns by increasing his speed by 50%. What is his average speed for both the trips ?

Answer: Option C

Speed on return trip = 150% of 40 = 60 kmph
∴ Average speed :
$$\begin{array}{rl}& =\left(\frac{2\times 40\times 60}{40+60}\right)\text{kmph}\\ & =\left(\frac{4800}{100}\right)\text{kmph}\\ & =48\text{ kmph}\end{array}$$