A motorboat can maintain a constant speed of 12 miles per hour relative to the water. The boat makes a trip upstream in 40 minutes and the return takes 20 minutes. What is the speed of the current?
my answer was; 24 m/hr
thanks for help!
my answer was; 24 m/hr
thanks for help!
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Let v = speed of current.
The speed upstream is 12 - v, and the speed downstream is 12 + v. The speed downstream is twice the speed upstream since it takes half the time for the trip.
12 + v = 2(12 - v)
The answer couldn't be 24 mph because then you couldn't manage to go upstream at all. If your boat only goes 12 mph against a 24 mph current, you'll be going backward at 12 mph.
The speed upstream is 12 - v, and the speed downstream is 12 + v. The speed downstream is twice the speed upstream since it takes half the time for the trip.
12 + v = 2(12 - v)
The answer couldn't be 24 mph because then you couldn't manage to go upstream at all. If your boat only goes 12 mph against a 24 mph current, you'll be going backward at 12 mph.