SOLUTION: Hi! I am the father of an exasperated 9th grader. Thank you SO MUCH for being there! Here is the question that is stumping her:
A boat travels 35km upstream and then back again
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A boat travels 35km upstream and then back again
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Question 1060014: Hi! I am the father of an exasperated 9th grader. Thank you SO MUCH for being there! Here is the question that is stumping her:
A boat travels 35km upstream and then back again in 4 hours 48 minutes. If the speed of the boat in still water is 15km/hr, what is the speed of the current?
Thank you,
Tim in Massachusetts Answer by ikleyn(52815) (Show Source):
You can put this solution on YOUR website! .
Hi! I am the father of an exasperated 9th grader. Thank you SO MUCH for being there! Here is the question that is stumping her:
A boat travels 35 km upstream and then back again in 4 hours 48 minutes. If the speed of the boat in still water is 15 km/hr, what is the speed of the current?
Thank you,
Tim in Massachusetts
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Let "v" be the speed of the current, in km/h.
Then the speed of the boat traveling upstream is (15-v) km/h,
the speed of the boat traveling downstream is (15+v) km/h.
The time traveling 35 km upstream is hours.
The time traveling 35 km downstream is hours.
The total time is 4 hours 48 minutes = hour = hour = hour,
which gives an equation
= .
To solve it, multiply both sides by 5*(15-v)*(15+v). You will get
35*5*(15+v) + 35*5*(15-v) = 24*(225-v^2),
24v^2 = 24*225 - 2*35*5*15 = 150,
v^2 = = ,
v = = = 2.5 km/h.
Answer. The speed of the current is 2.5 km/h.
