SOLUTION: Hello i need you to help me with this problem, A boat traveled 21 miles upstream on a river in 7 hours. The return trip took the boat 3 hours. What is the rate of the current, in m

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Hello i need you to help me with this problem, A boat traveled 21 miles upstream on a river in 7 hours. The return trip took the boat 3 hours. What is the rate of the current, in m      Log On


   

Question 1026400: Hello i need you to help me with this problem, A boat traveled 21 miles upstream on a river in 7 hours. The return trip took the boat 3 hours. What is the rate of the current, in miles per hour?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39623) About Me  (Show Source):
You can put this solution on YOUR website!
                rate       time       distance
upstream         r-c        7          21
downstream       r+c        3          21

system%287r-7c=21%2C3r%2B3c=21%29

Most convenient is to use Elimination Method to solve for c.
system%2821r-21c=21%2A3%2C21r%2B21c=21%2A7%29
42c=21%2A7-21%2A3
.
.

Answer by ikleyn(52832) About Me  (Show Source):
You can put this solution on YOUR website!
.
Hello i need you to help me with this problem, A boat traveled 21 miles upstream on a river in 7 hours.
The return trip took the boat 3 hours. What is the rate of the current, in miles per hour?
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It is a typical Wind and Current word problem.

See the lesson More problems on upstream and downstream round trips in this site, Problem 1.

This problem is very similar to yours.

In that lesson you will find the detailed solution. 

Consider it as a sample. Read it attentively.

Then solve your problem by substituting your data.

In this way you will learn how to solve similar problems once and for all.