SOLUTION: The current in a river is 6 miles per hour. In her motorboat Marissa can travel 12 miles upstream or 16 miles downstream in the same amount of time. What is the speed of her motorb

Algebra ->  Equations -> SOLUTION: The current in a river is 6 miles per hour. In her motorboat Marissa can travel 12 miles upstream or 16 miles downstream in the same amount of time. What is the speed of her motorb      Log On


   

Question 612506: The current in a river is 6 miles per hour. In her motorboat Marissa can travel 12 miles upstream or 16 miles downstream in the same amount of time. What is the speed of her motorboat in still water?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Boat speed x mph
current speed 6 mph
..
against current x - 6 mph
with current x + 6 mph

Distance against current 12
Distance with current 16
Time = same equate the time against with time with current
t=d/r
12 /(x- 6 )= 16 /(x+ 6 )
12 *(x+ 6 )= 16 *(x- 6 )
12 x + 72 = 16 x -96
12 x -16 x = -96 + -72
-4 x = -168
/ -4
x= 42 mph
m.ananth@hotmail.ca