question_answer

A man swimming downstream overcome a float at a point M After travelling distance D he turned back and passed the float at a distance of D/2 from the point M, then the ratio of speed of swimmer with respect to still water to the speed of the river will be

A) 2                     

B) 3

C) 4                     

D) 2.5

Correct Answer: B

Solution :

[b] Time taken by man to go form M to P and then P to N = time taken by float to go form M to N. \[\frac{D}{v+u}+\frac{D}{2(v-u)}=\frac{D}{2u}\] Simplify to get \[\frac{v}{u}=3\]