Question

John covers a part of the journey at $20\frac{km}{hr}$ and the remaining at $70\frac{km}{hr}$, taking total of 8 hours to cover the distance of 400 km. How many hours has he been driving at $20\frac{km}{hr}$?

• A. 2 hours
• B. 3 hours 20 minutes
• C. 4 hours 40 minutes
• D. 3 hours 12 minutes

Answer 1

The correct option is D

3 hours 12 minutes

Let the total time he travelled with a speed of 20 $\frac{km}{hr}$ is x hr.

So at 70 $\frac{km}{hr}$ he travelled = 8-x

So, 20x + 70(8-x) =400

The total distance traveled = 20x + 560 - 70x = 400

50x = 160

x = 3.2 hrs

i.e. 3 hours 12 minutes