Does anyone know how to work a word problem about current when the time for each distance is different but you only know the total amount of time for the whole trip i.e. the trip upstream and back to 5 hours and 20 minutes with a current of 3KMPH

Question

tad1 · Answer

use d= rt, setting the distances equal. Distance upstream is equal to the distance downstream.  the the current is x mph.  so if the boat is rowing upstream, the rate would be rate - x.  If the boat is rowing downstream the rate would be r + x.Hopefully you know either how fast the rower is rowing or you know one of the times.  Hope this helps.

anonymous · Answer

Thank you for your answer.  But that is my problem.  I know the total trip is 24 miles, so 12 miles each way.  And I know the current is 3mph.  And I know the entire trip was 5 hours and 20 minutes, but I don't know anything else.  The question is how fast could Bob row in still water.  I'm having difficulty because the times for the two trips cannot be the same.  Thanks again for your help.

tad1 · Answer

The rate  up would be decreased by the current the same amount the rate would be increased going downstream.  So r would be constant in still water. So 2r(5 h 20 min) = 24

anonymous · Answer

I think you are meant to assume that the speed going one way will be reduced by 3kmph, and increased going the other way by the same amount. I.E. The speed he rows is constant. Going upstream it will be (v-3)t  and going downstream will be (v+3)t

anonymous · Answer

So you have a system and can solve for some of the unknowns.

tad1 · Answer

We are saying the same thing.  Just solve the above equation for r.

anonymous · Answer

Thank you.  That has really helped.