A delivery van travels at a constant speed of 60 km/h to cover a certain route in 1 hour 45 minutes. If traffic increases the time taken by 15 minutes, by what percentage must the van's average speed decrease to complete the route?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 12.5%.
Time = 1 hr 45 min = 1.75 hr
Distance = speed × time = 60 × 1.75= 105 km
New time = 1 hr 45 min + 15 min = 2 hr
New speed = distance/time = = 52.5 km/h
Decrease in speed = 60 − 52.5 = 7.5
Percentage decrease = × 100 = 12.5%