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Question 177121This question is from textbook Algebra and Trigonometry: Structure and Method
: I have been tackling rational expressions and word problems as of late, but I'm not entirely sure where to get started on this particular problem. Any help would be much appreciated!
Bill rowed 30km upstream against a 2km/h current and back again in a total of 8 hours. How fast can he row in still water?
This question is from textbook Algebra and Trigonometry: Structure and Method
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! I have been tackling rational expressions and word problems as of late, but I'm not entirely sure where to get started on this particular problem. Any help would be much appreciated!
Bill rowed 30km upstream against a 2km/h current and back again in a total of 8 hours. How fast can he row in still water?
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If r is his speed in still water (or relative to the water, same thing),
Upstream, his speed was r-2
Downstream, it was r+2
time = distance/rate
time upstream = 30/(r-2)
time downstream = 30/(r+2)
(30/(r-2)) + (30/(r+2)) = 8
Multiply by (r-2*(r+2)
30*(r+2) + 30*(r-2) = 8r^2 - 32
60r = 8r^2 - 32
2r^2 - 15r - 8 = 0
(2r + 1)*(r - 8) = 0
r = 8, r = -1/2 (ignore the -1/2)
speed = 8 kph
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