SOLUTION: A boat travels 36 miles downstream (with the current) and returns the same distance upstream (against the current). The boat's speed was 15 mph. If round trip took 5 hours, determi

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A boat travels 36 miles downstream (with the current) and returns the same distance upstream (against the current). The boat's speed was 15 mph. If round trip took 5 hours, determi      Log On


   

Question 930545: A boat travels 36 miles downstream (with the current) and returns the same distance upstream (against the current). The boat's speed was 15 mph. If round trip took 5 hours, determine the speed of the current.
ANSWER: The speed of the current is ____ mph.
Answer by mananth(16946) About Me  (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 = 36 miles Total Time= 5.00 hours
Time upstream + time downstream = 5 hours

36 /( 15 - x )+ 36 /(
36 ( 15 + x )+ 36 (
540 + 36 x + 540 -36 x
1080 - -1125 = -5 X^2
-45 = -5 X^2
-5 X^2= -45
x2= = 9
x= +/- 3
3 mph