A boat travels 16 miles upstream and 15 miles downstream. The total time for both parts of the trip is 9 hours. The speed of the boat in still water is 9 mph. Find the speed of the current.

let x be the speed of the current:

16 = (9 - x)t

t= 16/(9 - x)

substitute t into equation below:

15 = (9 + x)(9- t) ----> -9x

^{2 }-x + 450 use quadratic formula ---> [1 ± √[1 - 4*(-9)*450]]/2*(-9)so x ≈

**7.016miles/hour**
## Comments