SOLUTION: A boat traveled 15 mph in still water. It traveled 20 mi upstream and back in a total of 3 hour. What is the speed of the current?

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Question 806074: A boat traveled 15 mph in still water. It traveled 20 mi upstream and back in a total of 3 hour. What is the speed of the current?
Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website!
boat speed = 15 mph
current speed = x mph

against current = 15 - x
with current = 15 + x

Total distance = 20 miles Total Time= 3.00 hours
Time upstream + time downstream = 3 hours

20 /( 15 - x )+ 20 /( 15 + x )= 3
20 ( 15 + x )+ 20 ( 15 - x )= 3.00 ( 225 - 1 X^2 )
300 + 20 x + 300 -20 x = 675 - 3 X^2
600 - -675 = -3 X^2
-75 = -3 X^2
-3 X^2= -75
X^2 = 25
X = +/- 5
ignore negative
current speed = 5 mph