SOLUTION: A boat traveled 72 miles downstream and back. The trip downstream took 3 hours. The trip back took 12 hours. Find the speed of a boat in still water and the speed of a current.
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Question 549707: A boat traveled 72 miles downstream and back. The trip downstream took 3 hours. The trip back took 12 hours. Find the speed of a boat in still water and the speed of a current.
You can put this solution on YOUR website! Boat speed =x mph
current speed =y mph
against current , x-y 12 hours
with current , x+y 3 hours
Distance = same= 72 miles
t=d/r against current
72 / ( x - y )= 12.00
12 ( x - y ) = 3.00
With current
12 x -12 y = 72 ....................1
72 / ( x + y )= 3.00
3.00 ( x + y ) = 72
3.00 x + 3 y = 72 ...............2
Multiply (1) by 1.00
Multiply (2) by 4.00
we get
12 x + -12 y = 72
12 x + 12 y = 288
24 x = 360
/ 24
x = 15 mph
plug value of x in (1)
12 x -12 y = 72
180 -12 y = 72
-12 y = 72 -180
-12 y = -108
y = 9 mph
Boat 15 mph
current 9 mph
