Asked by Devin
The time it takes you to go 12 miles upstream is 5/4 the time it takes you to go 14 miles downstream. If the current is 3mph, how fast do you go in still water.
Answers
Answered by
Reiny
speed in still water --- x mph
time upstream = 12/(x-3)
time downstream = 14/(x+3)
12/(x-3) = (5/4)(14/(x+3))
70(x-3) = 48(x+3)
70x - 210 = 48x + 144
22x = 354
x = 16.09 mph
check
time against current = 12/13.09 = .91673
time with current = 14/19.09 = .733368
.91673/.733368 = 1.25003 , not bad for 5/4
time upstream = 12/(x-3)
time downstream = 14/(x+3)
12/(x-3) = (5/4)(14/(x+3))
70(x-3) = 48(x+3)
70x - 210 = 48x + 144
22x = 354
x = 16.09 mph
check
time against current = 12/13.09 = .91673
time with current = 14/19.09 = .733368
.91673/.733368 = 1.25003 , not bad for 5/4
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