SOLUTION: a motor boat can travel 9 miles/h up a river, and back downstream at 15 miles/h. find the rate of the motorboat in still water and the rate of the water current?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: a motor boat can travel 9 miles/h up a river, and back downstream at 15 miles/h. find the rate of the motorboat in still water and the rate of the water current?      Log On


   

Question 628752: a motor boat can travel 9 miles/h up a river, and back downstream at 15 miles/h. find the rate of the motorboat in still water and the rate of the water current?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +b+ = speed of boat in still water
Let +c+ = speed of water current
given:
(1) +b+-+c+=+9+
(2) +b+%2B+c+=+15+
---------------
Add the equations
+2b+=+24+
+b+=+12+
and
(2) +12+%2B+c+=+15+
(2) +c+=+15+-+12+
(2) +c+=+3+
The speed of the boat in still water is 12 mi/hr
The speed of the water current is 3 mi/hr