Two buses start from the same station at 9.00am and travel in opposite directions along the same straight road. The first bus travel at a speed of 72 km/h and the second at 48 km/h. At what time will they be 240km apart?

A.

1:00 pm

B.

12:00 noon

C.

11:00 am

D.

10:00 am

Correct answer is C

Let x be the time 

Then 72x + 48x = 240 

\(\frac{120}{120} \times \frac{240}{120}\)

x = 2hrs

9:00 + 2hrs = 11:00 am