I'm not asking you to do it, I just need help.
Let r=rate in km/h of a rowboat in still water, and c=rate in km/h of a streams current. Write an equation to express that it takes 2 hrs to row the boat 20 km upstream.
2007-04-23 12:12:36 · 4 answers · asked by Heather J 2 in Science & Mathematics ➔ Mathematics
DIRT: Distance Is Rate (times) Time.
The speed of the boat going upstream is (r - c) km/hr.
As it takes 2hr to row 20km upstream, your equation is:
20 = (r - c) * 2.
2007-04-23 12:20:06 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The rate of the boat upstream will be the rate of rowing less the rate of the stream. Divide the distance by this new rate.
2007-04-23 12:22:35 · answer #2 · answered by Helmut 7 · 0⤊ 0⤋
Traveling upstream, the boat has r velocity and the stream has -c velocity
V = r-c
v=d/t
r-c = d/t
r-c = 20/2
r-c = 10
2007-04-23 12:19:59 · answer #3 · answered by Math Guy 4 · 0⤊ 0⤋
distance =rate x time
d = 20 km
total rate r' = r-c
t = d/r' = 20km/(r-c) = 2 hr
2007-04-23 12:23:54 · answer #4 · answered by kellenraid 6 · 0⤊ 0⤋