Question

A car travels a total distance of 150 miles. The speed of a car is 20 miles per hour for the first three hours and 30 miles per hour for the remaining $t$ hours. Find the total time taken by the car (in hours) to cover the distance. (Hint: Distance = speed × time)

• A. 6 h
• B. 4 h
• C. 3 h
• D. 5 h

Answer 1

The correct option is A 6 h

Total distance covered by the car = 150 mi
We know, distance = speed × time

For the first 3 hours:
Speed = 20 mi per h
Distance covered in the first 3 hours = speed of the car × time taken
$=20\times 3=60mi$

For the next $t$ hours:
Speed = 30 mi per h
Distance covered in the next $t$ hours = speed of the car × time taken
$=30\times t=30t$ $mi$

Total distance covered by car = distance covered in the first 3 hours + distance covered in the next $t$ hours
$\Rightarrow 150=60+30t\Rightarrow 150-60=30t\Rightarrow 30t=90\Rightarrow t=\frac{90}{30}=3h$
Hence, the total time taken by the car is 3 + 3 = 6 hours.