Asked by Marina
I am having a hard time with this question.
A boat went 15 miles downstream in 1 hour and then returned upstream to its dock in 5/3 hours. if the current of the stream was constant, find the speed of the boat in still water and the speed of the current
A boat went 15 miles downstream in 1 hour and then returned upstream to its dock in 5/3 hours. if the current of the stream was constant, find the speed of the boat in still water and the speed of the current
Answers
Answered by
Reiny
speed of boat in still water --- x mph
speed of current ---------- y mph
so speed against the current = x-y mph
and speed with the current = x+y mph
downstream(with the current)
15/(x+y) = 1
x+y = 15
upstream:
15/(x-y) = 5/3
5x - 5y = 45
x - y = 9
add them:
2x = 24
x = 12, then since x+y=15, y = 3
speed of boat is 12 mph, the current is 3 mph
speed of current ---------- y mph
so speed against the current = x-y mph
and speed with the current = x+y mph
downstream(with the current)
15/(x+y) = 1
x+y = 15
upstream:
15/(x-y) = 5/3
5x - 5y = 45
x - y = 9
add them:
2x = 24
x = 12, then since x+y=15, y = 3
speed of boat is 12 mph, the current is 3 mph
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