A takes 4 h more than the time taken by B to walk D km. If A doubles his speed, he can make it in 2 h less than that of B. How much time does B require for walking D km?
Correct Answer: 8 h
Explanation:
Let B takes x h to walk D km.
Then, A takes ( x + 4 ) h to walk D km.
With doube of the speed,
A will take ( x+ 4)/2 h. According to the question,
x - (x + 4)/2 = 2
⇒ 2x - (x + 4) = 4
⇒ 2x - x - 4 = 4
∴ x = 4 + 4 = 8 h
