SOLUTION: A boat can go 63 mph in still water. It takes as long to go 120 miles upstream as it does to go 150 miles downstream. What is the current?

Question 462476: A boat can go 63 mph in still water. It takes as long to go 120 miles upstream as it does to go 150 miles downstream. What is the current?
Found 2 solutions by rwm, josmiceli:
Answer by rwm(914) (Show Source): You can put this solution on YOUR website!
(63+x)*t=150
t=150/(63+x)
(63-x)*t=120
t=120/(63-x)
150/(63+x)=120/(63-x)
120*(63+x)=150*(63-x)
x=7 mph current
BTW t=15/7
(63+7)*15/7=150
10*15=150
ok
(63-7)*15/7=120
56/7*15=120
8*15=120
ok

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = speed of current
Let = time to go either upstream or downstream
given:
Speed in still water = mi/hr
Going upstream, speed =
Going downstream, speed =
Upstream:
(1)
Downstream:
(2)
Add the equations

hrs
Substitute in (2)
(2)
(2)
(2)
(2)
The speed of the current is 7 mi/hr
check:
(1)
(1)
(1) (rounding off error)
OK
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