A car covers three equal distances at speeds of 30 km/h, 45 km/h, and 90 km/h, respectively. What is the average speed of the car for the entire journey?
Show answer & explanation
Correct answer: D
Explanation
Given:
Speed = 30 km/h
Speed = 45 km/h
Speed = 90 km/h
Average speed = (3 × 30 × 45 × 90) / (30 × 45 + 45 × 90 + 90 × 30)
= (3 × 121500) / (1350 + 4050 + 2700)
= 364500 / 8100
= 45 km/h