A person travels a total distance of 480 km, partly by car at a speed of 80 km/h and the rest by bike at 40 km/h. If 75% of the total distance is covered by car, find the approximate average speed of the entire journey.
Show answer & explanation
Correct answer: D
Explanation
Given:
Total distance = 480 km
Speed of car = 80 km/h
Speed of bike = 40 km/h
Distance by car = 75%
Distance by car = 75% × 480 = 360 km
Distance by bike = 480 − 360 = 120 km
Time by car = 360 / 80 = 4.5 hours
Time by bike = 120 / 40 = 3 hours
Total time = 4.5 + 3 = 7.5 hours
Average speed = 480 / 7.5 = 64 km/h