A car travels three equal distances at the speed of 10 km/hr, 15 km/hr and 40 km/hr respectively. What is the average speed (in km/hr) for this journey?
Show answer & explanation
Correct answer: B
Explanation
Given:
Speed₁ = 10 km/h
Speed₂ = 15 km/h
Speed₃ = 40 km/h
According to the formula:
Average speed for equal distances = 3 / (1/v₁ + 1/v₂ + 1/v₃)
= 3 / (1/10 + 1/15 + 1/40)
= 3 / ((12 + 8 + 3)/120)
= 3 / (23/120)
= 3 × 120 / 23
= 360 / 23