A man covers half part of a certain distance at 60 km/hr. He covers 40 percent of the remaining distance at the speed of 12 km/hr and covers the rest of the distance at the speed of 18 km/hr. What is his average speed for the entire journey?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 24 km/hr.
Concept used:
Average speed = Total distance/Total time
Calculations:
Let the total distance be 10D
Distance travelled at 60 km/h = 5D
Distance travelled at 12 km/h = 2D
Distance travelled at 18 km/h = 3D
According to the question;
⇒ Average speed = 10D/[(5D/60) + (2D/12) + (3D/18)]
⇒ Average speed = 10D/[(75D)/180]
⇒ Average speed = 24 km/h