contestada

The speed of a stream is 2 mph. A boat travels 7 miles upstream in the same time it takes to travel 11 miles downstream. What is the speed of the boat in still​ water?

Respuesta :

4 = (r-2) t

8 = (r+2) t

4 = (r-2) * [8/(r+2)]

4 = (8r-16)/ (r+2)  . . .multiply by 2


4r + 8 = 8r - 16

4r = 24

r = 6