Question

A car starts at P, and travels at a speed of 50 $km{h}^{-1}$ for 6 hours. It comes to rest at Q. 2 hours after the first car starts, another car starts at P and moves towards Q.
In order to reach the point Q at the same time as the first car, with what speed must the second car travel?

• A. 65 $km{h}^{-1}$
• B. 75 $km{h}^{-1}$
• C. 85 $km{h}^{-1}$
• D. 55 $km{h}^{-1}$

Answer 1

The correct option is B 75 $km{h}^{-1}$

Given:
Speed of first car = $50km{h}^{-1}$
Time travelled by the first car = 6 h.

$\therefore$ Distance between P and Q = $50\times 6=300km$

Now, the second car starts 2 hours after the first car.
To reach the point Q at the same time as the first car, the second car should cover the distance between P and Q in the remaining time.

Distance to be covered = 300 km
Remaining time = 6 - 2 = 4 h

Required speed = $\frac{300}{4}$ = $75km{h}^{-1}$