A person travels from P to Q at a speed of 50 km/h and returns by increasing his speed by 60%. What is his average speed for both the trips?

Speed from P to Q = 50 km/h

Speed for return trip = 60 % increase in previous speed

The formula for average speed when the distance is the same for both trips is:

​$$\text{Average speed} = \frac{2 \times S_1 \times S_2}{S_1 + S_2}$$​​

Where:

$$S_1$$​ is the speed while going,

$$S_2$$ is the speed while returning.

Return speed = $$50 \times \frac{160}{100} = 80 km/h$$​ 

By applying the formula,

Average speed = $$\frac{2 \times 50 \times 80}{50 + 80}$$ = $$\frac{8000}{130} = 61.53km/h$$ 

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