Anup cam row 33 km downstream and 35 upstream in 8 hours. He can also row 44 km downstream and 28 km upstream in the same time. How much time (in hours) will be take to row 55 km downstream and 14 km upstream?

7

Let the speed of river be “x” and speed of boat be “y”.

Downstream speed = x + y

Upstream speed = x – y

Here, according to the question, 

= 33/(x + y) + 35/(x - y) = 8

and 44/(x + y) + 28/(x - y) = 8

As the number of required hours is a complete number hence 

The values of (x + y) & (x - y) should divide the respective numbers

For Downstream, that is 33 and 44 both are multiples of 11

and for Upstream, that is 35 and 28 both are multiples of 7

By value putting method, 

= 33/11 + 35/7 = 3 + 5 = 8 & 44/11 + 28/7 = 4 + 4 = 8

= x + y = 11 & x - y = 7

Required time, = 55/11 + 14/7 = 5 + 2 = 7 hours