SOLUTION: The current in a stream moves at a speed of 7 mph. A boat travels 38 mi upstream and 38 mi downstream in a total time of 3 hr. What is the speed of the boat in still​ water?
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Question 1057506: The current in a stream moves at a speed of 7 mph. A boat travels 38 mi upstream and 38 mi downstream in a total time of 3 hr. What is the speed of the boat in still water?
And,
The outside of a picture frame measures 14 in by 20 in. 184 in. squared of the picture shows. Find the thickness of the frame. Found 2 solutions by josgarithmetic, ikleyn:Answer by josgarithmetic(39620) (Show Source):
SPEED TIME DISTANCE
UPSTREAM r-7 38/(r-7) 38
DOWNSTR r+7 38/(r+7) 38
Total 3
Uniform width of frame, ok, but not enough information for its thickness.
Width of frame instead: ;
which is, the given picture area is equal to the inner frame area.
You can put this solution on YOUR website! .
The current in a stream moves at a speed of 7 mph. A boat travels 38 mi upstream and 38 mi downstream in a total time of 3 hr.
What is the speed of the boat in still water?
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Let "u" be the speed of the boat in still water.
Then the boat speed moving downstream is (u+7) mph,
while the speed moving upstream is (u-7).
The time traveling upstream is hours.
The time traveling downstream is hours.
The total time for the round trip is + hours.
And the equation is
+ = 3. ("time" equation).
To solve it, multiply both sides by (u-7)*(u+7).
You will get
38*(u+7) + 38*(u-7) = .
Simplify:
= ,
= 0.
Solve using the quadratic formula
= = .
We are interested in positive root only.
It is u = =~ 13.569 km/h (approximately).
Check. + = 3.000 hours.
Answer. The boat speed in still water is 13.569 km/h (approximately).
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