Mohan completed a certain journey by car. If he covered 30% of the distance at 90 km/h, 45% of the distance at 135 km/h and the remaining distance at 75 km/h. His average speed (in km/h) for the entire journey is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 100.
Average Speed = Total distance/Total time
Let the distance be 100 units
He covered 30% of the distance at 90 km/h = 30 units
45% of the distance at 135 km/h = 45 units
Remaining distance = 100 - (45 + 30) = 25 units covered with a speed of 75 km/h
According to the question
Total time = (30/90) + (45/135) + (25/75) = 1/3 + 1/3 + 1/3 = 1 hour
The average speed = 100/1 = 100 km/h