A motor car starts with a speed of 60 km/h and increases its speed after every two hours by 15 km/h. In how much time will it cover a distance of 450 km?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1, i.e., 6 hours.
Initial speed, u = 60 km/h
Increase in speed every 2 hours = 15 km/h
Speeds in each 2-hour interval:
First 2 hours: 60 km/h
Second 2 hours: 60 + 15 = 75 km/h
Third 2 hours: 75 + 15 = 90 km/h
Distance covered in each 2-hour interval:
Distance = speed × time
First 2 hours: 60 × 2 = 120 km
Second 2 hours: 75 × 2 = 150 km
Third 2 hours: 90 × 2 = 180 km
Total distance after 6 hours: 120 + 150 + 180 = 450 km
Time taken = 6 hours