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).
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 53.33.
Distance P → Q = 60 km
Time = 45 min = 0.75 hr → speed = 60 ÷ 0.75 = 80 km/hr (matches)
Return journey speed = 40 km/hr
Average speed = (2 × S1 × S2) ÷ (S1 + S2)
= (2 × 80 × 40) ÷ (80 + 40)
= (6400) ÷ 120 = 53.33 km/hr