SOLUTION: a boat traveled downstream a distance of 72 mi and then came right back. If the speed of the current at 7 mph and the total trip took 3 hours, find the average speed of the boat re
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Question 786281: a boat traveled downstream a distance of 72 mi and then came right back. If the speed of the current at 7 mph and the total trip took 3 hours, find the average speed of the boat relative to the water
Answer by josgarithmetic(39632) (Show Source): You can put this solution on YOUR website!
r = speed of boat without any river current
DIRECTION_________rate_____________time__________distance
down_____________r+7_______________(___)_________72
up_______________r-7_______________(___)_________72
Total________________________________3
Key concept among the numbers where r is rate, t is time, d is distance. Using this formula allows us
DIRECTION_________rate_______________time__________distance
down_____________________________________72
up_______________________________________72
Total_________________________________3
The time sum should be obvious.
Multiply left and right by , and THEN continue to simplify, finally solving for r.
Alternatively,
-------(maybe you could keep intermediate steps
-Use general solution to quadratic formula-
Boat speed in still water, 49 mph.
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