Word problem

Question

Casey can travel 8 miles upstream in the same time it takes her to go 12 miles downstream. Her boat goes 15 mph in still water. What is the rate of the current?

Answer 1

distance = rate x time

 

S is the speed of the current

 

 

8 = (15 - s) x t

 

12 = ( 15 + s ) x t

 

 

  8 = 15t - st

12 = 15t + st

 

 

20 = 30t

 

2/3= t, which is 40 minutes

 

8 = (15 - s)*2/3

 

8 * 3/2 = 15 -s

 

12 = 15 - s

 

12 - 15 = -s

 

-3 = -s

 

s = 3

 

CHECK:   (15+3)*2/3 = 18 * 2/3 = 12

 

The speed of the current is 3 mph