Expert: Abe Mantell - 5/31/2007

Question
I know the basic travel problem can be solved through d=rt, but I don't know
how to solve the following question:
A family is canoeing downstream (with the current).Their speed
relative to the banks of the river averages 2.75 mi/h. During the return trip,

they paddle upstream (against the current), averaging 1.5 mi/h relative to

the riverbank.

a.

Write an equation for the rate of the canoe downstream.
b.

Write an equation for the rate of the canoe upstream.
c.

Solve the system to find the family's paddling speed in still water.
d.

Find the speed of the current of the river.

I do not understand how to reach an answer for this question.

Answer
Hello Katie,

Since the speeds are relative to the riverbanks
the downstream average speed is 2.75 mi/hr, and
the upstream average speed is 1.5 mi/hr.

So I am not sure what you are asking.  If the speed of
the canoe upstream & downstream are the same relative to
the water, then we can write...
x+y=2.75 and
x-y=1.5, where x=canoe speed & y=stream speed
Solving gives x=2.125 and y=0.625

OK?

Abe