<PRE><B>Question 110987</B>
Kelley&#39;s boat goes 12 mph. Find the rate of the current of the river, if she can go 6 mi upstream in the same amount of time she can go 10 mi downstream.
:
Let x = rate of the currents
Then:
(12+x) = speed downstream
and
(12-x) = speed upstream 
:
Time = Dist/speed
:
Up time = down time
{{{6/(12-x)}}} = {{{10/(12+x)}}}
:
Cross multiply:
6(12+x) = 10(12-x)
:
72 + 6x = 120 - 10x
:
6x + 10x = 120 - 72
16x = 48
x = 48/16
x = 3 mph speed of the current
:
:
Check solution by confirming the times are the same:
10/15 = 2/3 hr
6/9 = 2/3 hr</PRE>