The speed of a boat in still water is 15 km/h. The speed of the current is 3 km/h. In how much time(in hours) will the boat travel a distance of 54 km upstream and the same distance downstream?

$7\frac{1}{2}$

Upstream speed = ( 15 - 3 ) = 12 km/h

Downstream Speed = ( 15+ 3 ) = 18 km /h

According to question ,

 Time = \(\frac{54}{12}\) + \(\frac{54}{18}\)

= \(\frac{9}{2}\) + 3

= 7\(\frac{1}{2}\) hours