SOLUTION: I need help solving this problem. A paddle boat can move at a speed of 4km/h in still water. The boat is paddled 14km downstream in a river in the same time it takes to go 7km

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Question 923611: I need help solving this problem.
A paddle boat can move at a speed of 4km/h in still water. The boat is paddled 14km downstream in a river in the same time it takes to go 7km upstream. What is the speed of the river?
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
we have two formulas here using rate*time = distance, let x be speed of the river and t be time
(4+x)*t = 14
(4-x)*t = 7
from these two equations we have two expressions for t
t = 14 / (4+x)
t = 7 / (4-x)
set the two expressions equal to each other and solve for x
14 / (4+x) = 7 / (4-x)
cross multiply the fractions
14*(4-x) = 7 * (4+x)
divide both sides of = by 7
2*(4-x) = (4+x)
8-2x = 4+x
3x = 4
x = 4/3 = 1.33 km/h