A bus goes from city P to Q in 45 minutes, covering a distance of 60 km, and comes back to city P with a speed of 40 km/hr. The average speed of the bus in the journey is _____ km/hr (correct to two decimal places).

Correct option is D

Given:
Distance from City P to Q = 60 km
Time taken from P to Q = 45 minutes = 0.75 hours
Return speed from Q to P = 40 km/hr
Concept Used:
​$$\text{Average Speed} = \frac{2 \times \text{Speed}_1 \times \text{Speed}_2}{\text{Speed}_1 + \text{Speed}_2}$$​​
Solution:
​$$\text{Speed}_1 = \frac{\text{Distance}}{\text{Time}} = \frac{60}{0.75} = 80 \, \text{km/hr}$$​​
Speed₂ = 40 km/hr
Average Speed = $$\frac{2 \times 80 \times 40}{80 + 40} = \frac{6400}{120} = 53.33 \, \text{km/hr}$$​​