Question

A man can row 5 km upstream and 3 km downstream in 35 hrs .also he can row 2 km upstream and downstream in 28 hrs .what is the speed of man in still water

Answer 1

we know , downstream means the direction along the stream while upstream means the direction against the stream.

Let the speed of man in still water = x km/h
speed of the stream = y km/h

so, downstream $\implies$ (x + y) km/h
upstream $\implies$ (x - y) km/h

a/c to question,
A man can row 5 km upstream and 3 km downstream in 35 hrs.

e.g., 5/(x + y) + 3/(x - y) = 35 ........(1)

again, the man can row 2 km upstream and downstream in 28 hrs.

e.g., 2/(x + y) + 2/(x - y) = 28.......(2)

solve equations (1) and (2),

4/(x + y) = 70 - 84 = negative

but x and y are speed so, can't be negative. it seems your data is incomplete. plz again check your question and mentioned . I will edit then answer.

well, I explained the required concepts , you can also solve by using above mentioned method.