Question

A man rows 20 km downstream in 2 hours and upstream 4km in 2 hours. Find the speed of the current

Answer 1

The speed of the rowing on still water denoted by M kmph.

The speed of the stream denoted by N kmph.

The upstream speed of Ritu’s rowing is (M – N) kmph

The downstream speed of Ritu’s rowing is (M + N) kmph

2(M+N)=20     _______________________ (1)  

2(M-N)=4       ________________________ (2)

Solving the equation, we get  

2(M+N)=20;

2(M-N)=4;  

M-N=2;

M=2+N;

Substituting M=2+N in equation (1)

2(M+N)=20

2(2+N+N)=20 ;  

N=4  

Substituting N = 4 in equation (1),  

2(M+N)=20

2(M+4)=20

2M+8=20

2M=20-8

2M=12

M=6  

the value of M = 6.

Therefore, the speed at which Ritu rows is 6 kmph and the speed of the current is 4 kmph.