SOLUTION: A boat going across a lake 8 km wide proceeds 2 km at a certain speed and then completes the trip at a speed of 0.5 km/hr faster. By doing this, the boat arrives 10 minutes earlier

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Question 896125: A boat going across a lake 8 km wide proceeds 2 km at a certain speed and then completes the trip at a speed of 0.5 km/hr faster. By doing this, the boat arrives 10 minutes earlier then if the original speed had been maintained. Find the original speed of the boat.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A boat going across a lake 8 km wide proceeds 2 km at a certain speed and then completes the trip at a speed of 0.5 km/hr faster.
By doing this, the boat arrives 10 minutes earlier then if the original speed had been maintained
Find the original speed of the boat.
:
let s = the original speed
then
(s+.5) = the faster speed for last 6 km of the trip
change 10 min to 1/6 hr
:
Find the time it took at the two speed
2%2Fs + 6%2F%28s%2B.5%29 = %282%28s%2B.5%29%2B6s%29%2F%28s%28s%2B.5%29%29 = %282s%2B1%2B6s%29%2F%28s%28s%2B.5%29%29 = %288s%2B1%29%2F%28s%28s%2B.5%29%29
Find s when the difference is 10 min
8%2Fs - %288s%2B1%29%2F%28s%28s%2B.5%29%29 = 1%2F6