Question
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
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