A man can row a distance of 8 km downstream in a certain time and can row 6 km upstream in the same time. If he rows 24 km upstream and the same distance downstream in $1 \frac{3}{4}$ hours, then the speed (in km/h) of the current is:

4

We know that,

Speed = D/t

D= Distance

t = time

We have,

Total distance = 24km

Time taken = 7/4 hours

Let the speed of man and current be v and s respectively. 

According to the question,

8/(v+s) = 6/(v−s)

= 8v - 8s = 6v + 6s

= 2v = 14s

= v : s = 7 : 1

Let speed of man = 7x

Speed of current = x

So,

24/8x + 24/6x = 7/4

= 3/x + 4/x = 7/4

= 7/x = 7/4

= x = 4

= speed of the current = 4 km/h