A man can row 5kmph in still water. If the river is running at 1kmph,
it makes him 75minutes to row to a place and back. How far is the place?
3 km
4 km
5 km
None of these
Explanation:
Speed in still water , ½ (a+b) = 5 == > a+b = 10 -- (1)
Speed of the stream , ½ (a-b) = 1 è a-b = 2 --(2)
Solving 1 and 2 gives a=6 ; b=4
Let the required distance be x km
x/6 + x / 4 = 75/60 == > 10x/24 = 75/60
x = 24x 75/10x60 = 3
required distance = 3 km
Speed in still water , ½ (a+b) = 5 == > a+b = 10 -- (1)
Speed of the stream , ½ (a-b) = 1 è a-b = 2 --(2)
Solving 1 and 2 gives a=6 ; b=4
Let the required distance be x km
x/6 + x / 4 = 75/60 == > 10x/24 = 75/60
x = 24x 75/10x60 = 3
required distance = 3 km