SOLUTION: A motorboat travels145 mi in 5 hours going upstream. It travels 215 going downstream in the same amount of time. What is the rate of the boat in still water and what is the rate

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Question 783860: A motorboat travels145 mi in 5 hours going upstream. It travels 215 going downstream in the same amount of time. What is the rate of the boat in still water and what is the rate of the current?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Let r = speed of boat in still water
let c = speed of the current

Direction___________speed__________time____________distance
UP__________________r-c____________5_______________145
DOWN________________r+c____________5_______________215

Most basically, r*t=d so we form two equations from the data table.
(r-c)5=145 and (r+c)5=215
5r-5c=145 and 5r+5c=215

Solve the system:
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5r-5c=145
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5r+5c=215
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Best way to begin solving the system is sum the lefthand members, sum the righthand members, and equate these. You would then immediately find the value for r. Continue any reasonable way to solve for and find c.