Question

If a man's speed with and against water current in a river be 15 km/ hr and 5km / hr ,then find the man's speed in still water and the speed of the river?

Answer 1

Let man's speed in still water = x km/h
river's speed = y km/h

man's speed with the current = 15 km/h
⇒ x + y = 15 
man's speed against the current = 5 km/h
⇒ x - y = 5 

Add the both
2x = 15+5 = 20
⇒ x = 10 km/h
y = 15 - x  =15-10 = 5 km/h

Speed of man in still water = 10 km/h
speed of river = 5 km/h

Answer 2

let the speed of man in still water be x

and speed of river be y

ATQ,

in first case

x+y=15-----------------(1)

in 2nd case

x-y=5--------------------(2)

after solving eq.1 and eq.2 we get

2x=20

x=10km/hr

now put value of x in eq. 1

10+y=15

y=15-10

y=5km/hr

hope it may help you