question_answer

A walks at a uniform rate of 4 km per hour and 4 hours after his start, B cycles after him at a uniform rate of 10 km per hour. How far from the starting point will B catch A?

A) 16-7 km            

B) 18-6 km

C) 21-5 km            

D) 26-7 km

Correct Answer: D

Solution :

Let B catch A with x km far from the starting point. Then,              \[\frac{x}{10}=\frac{x-4\times 4}{4}\]               \[\begin{align}   & 4x=10x-160 \\  & 6x=160 \\  & x=26.7\,\,km \\ \end{align}\]