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 he has been driving at $70\frac{km}{hr}$?

• 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 that he travelled with a speed of $20\frac{km}{hr}$ be x hours.

So, at $70\frac{km}{hr}$ he travelled for 8-x hours.

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.