Question 271802
 it takes bob the boy scout 10 hours to paddle upstreamin a distance of 15 miles.when he turns around he finds it only takes him 5 hours to paddle 22.5 miles with the current. Hoow fast is bob's boat going in still water and what is the speed of the current of the river?

Let x be the speed in still water and c the current.

1.) 15 = (x-c)*10
2.) 22.5 = (x+c)*5

Expanding:

1.) 15 = 10x - 10c
2.) 22.5 = 5x + 5c

Multiply equation 2.) by 2:

2.) 45 = 10x + 10c
1.) 15 = 10x - 10c

Add these two equations:

60 = 20x
x = 3