SOLUTION: Write and solve an equation: Eva is kayaking. In still water, she can travel 5 mph. She goes 4 miles downstream and 6 miles upstream in 3.5 hours. What is the speed of the current?

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Question 1057480: Write and solve an equation: Eva is kayaking. In still water, she can travel 5 mph. She goes 4 miles downstream and 6 miles upstream in 3.5 hours. What is the speed of the current? (Please show step by step)
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
               SPEED        TIME       DISTANCE

DOWNSTR         5+c         4%2F%285%2Bc%29       4

UPSTRM          5-c         6%2F%285-c%29       6

Total                       3.5



Answer by ikleyn(52910) About Me  (Show Source):
You can put this solution on YOUR website!
.
Write and solve an equation: Eva is kayaking. In still water, she can travel 5 mph. She goes 4 miles downstream and 6 miles upstream in 3.5 hours.
What is the speed of the current? (Please show step by step)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

The governing equation is 

4%2F%285%2Bc%29+%2B+6%2F%285-c%29 = 3.5

where "c" is the speed of the current.


To solve it, multiply both sides by (5+c)*(5-c).
Then simplify and solve the quadratic equation for "c".

It is a typical Upstream and Downstream round trips word problem.
You can find similar fully solved problems on upstream and downstream round trips with detailed solutions in lessons
    - Wind and Current problems
    - More problems on upstream and downstream round trips
    - Selected problems from the archive on the boat floating Upstream and Downstream
in this site.

Read them attentively and learn how to solve this type of problems once and for all.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the section "Word problems", the topic "Travel and Distance problems".