SOLUTION: A certain river has a current of 3 miles per hour. A boat takes twice as long to travel upstream between two points as it does to travel downstream between the same two points. Wh

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Question 768095: A certain river has a current of 3 miles per hour. A boat takes twice as long to travel upstream between two points as it does to travel downstream between the same two points. What is the speed of the boat still in water?
A) 3 miles per hour
B) 6 miles per hour
C) 9 miles per hour
D) 12 miles per hour
E) the speed cannot be determined from the given information
Answer by josgarithmetic(39623) About Me  (Show Source):
You can put this solution on YOUR website!
Current of river, speed = c
Boat speed = r

Going WITH current, r+c.
Going AGAINST current, r-c.

Twice as long to go against as to go along, then highlight%28r-c=%281%2F2%29%28r%2Bc%29%29
You are given a value for c and you are asked to find the value for r.

r-c=r%2F2%2Bc%2F2
r-r%2F2=c%2F2%2Bc
r%281%2F2%29=%283%2F2%29c
r=%282%2F1%29%283%2F2%29c
highlight%28r=3c%29