Question 212378
A power boat can travel upstream on a river at 24km/h and downstream at 30km/h. How far upstream can it go if the round trip is to take 3 hours?


Let distance upstream and downstream be D


Since it'll take 3 hours for the round trip, and since the boat's speed upstream and downstream are 24 and 30 km/h, respectively, we'll have:


{{{D/24 + D/30 = 3}}}

{{{5D + 4D = 360}}} ------ Multiply equation by LCD, 120


9D  =  360

{{{D = 360/9 = 40}}}


Therefore, the distance upstream that the boat can go is {{{highlight_green(40)}}} km.