<PRE><B>Question 532803</B>
A motorboat takes 5 hours to travel 400km going upstream. The return trip takes 2 hours going downstream. What is the rate of the boat in still water and what is the rate of the current?
**
let x=rate of boat in still water
let c=rate of current
speed downstream=x+c
speed upstream=x-c
distance=travel time*speed (same for both directions)
..

..
5(x-c)=400
2(x+c)=400
..
5x-5c=400
2x+2c=400
..
10x-10c=800
10x+10c=2000
add
20x=2800
x=140 km/hr
2c=400-2x=400-280=120
c=60 km/hr
ans:
rate of boat in still water=140 km/hr
rate of current=60 km/hr</PRE>