Algebra (Work Problem)
posted by Ruth .
Susan's backyard has three faucets: A, B and C. If she turns on all three of them, it takes 380 minutes to fill the pool. If she turns on only A and B, it takes 570 minutes, and if she turns on only B and C, it takes 760 minutes. If she turns on only A and C, how long will it take (in minutes) to fill the pool?

1/a + 1/b + 1/c = 1/380
1/a + 1/b = 1/570
1/b + 1/c = 1/760
solve for a,b,c and you get
1/a + 1/c = 1/760 + 1/1140 = 1/456