A boat travels 24 m.p.h. in still water. It takes 5 hours to travel downstream & 7 hours to travel upstream. How fast is the water moving?
2007-11-07 14:42:25 · 2 answers · asked by malissa h 1 in Science & Mathematics ➔ Physics
let r be the speed of the current
Then (24+r) is the speed downstream
and (24-r) is the speed upstream.
The distance traveled in each case is the same:
(24 +r) 5 = (24 - r) 7
Solving for r:
120 + 5r = 168 - 7r
12r = 48
r=4 mph
2007-11-07 14:51:39 · answer #1 · answered by stevemorris1 5 · 0⤊ 0⤋
two equations here = same distance
down = (5x24) + (5x rate)
up = (7x24) - (7x rate)
add the rate downstream * subtract from upstream
THEREFORE
(5 times 24) + 5X = (7 tmes 24) - 7X
solve for X
half the problem is knowing how to set it up - after that - YOU
are home free
enjoy
2007-11-07 14:48:37 · answer #2 · answered by tom4bucs 7 · 0⤊ 0⤋