A vehicle covers 90 km with a speed of 45 km/h and then another 90 km with a speed of 85 km/h. What is the overall average speed of the vehicle?
Show answer & explanation
Correct answer: C
Explanation
First distance = 90 km
First speed = 45 km/h
Time = 90 ÷ 45 = 2 hours
Second distance = 90 km
Second speed = 85 km/h
Time = 90 ÷ 85 = 18/17 hours
Total distance = 90 + 90= 180 km
Total time = 2 + 18/17= 52/17 hours
Average speed = 180 ÷ (52/17)
= 180 × 17/52
= 765/13= 58.85 km/h