Question

Regina covers one part of the journey at the speed of 15 kmph and the rest at the speed of 50 kmph, thus covering a distance of 120 km in 5 hours. For how many hours is she driving at 15 kmph?

1. 3.71 hours
2. 5.8 hours
3. 2.45 hours
4. 1.5 hours

Answer 1

Correct Answer - Option 1 : 3.71 hours

Given

Total distance = 120

Regina covers 120 km in 5 hour

Formula

Speed = distance/time

Calculation

Let x be the number of hours he travels at 15 kmph.

⇒ Distance covered in this x hours = 15x km

He would have therefore, traveled the balance (5 - x) hours at 50 kmph. 

Distance covered in this (5 - x) hours = (5 - x) × 50

⇒ (250 - 50x) km

The total distance traveled = 15x + 250 - 50x = 120

⇒ 35x = 130

⇒ x = (130/40) hours = 3.71 hour

∴She will drive at 15 kmph for 3.71 hour