algebra
posted by Math Girl .
a tugboat goes 160 miles upstream in 20 hours. The return trip downstream takes 10 hours. Find the speed of the tugboat without a current and the speed of the current.

if the speed of the boat in still water is x, and the speed of the current is c, then, remembering that distance=speed*time,
20(xc)=10(x+c)
20x20c=10x+10c
10x=30c
x=3c
20(2c) = 160
c = 4
so, x=12
check:
20(8) = 160
10(16) = 160