SOLUTION: It takes John and his wife Tracey 3.5 hours to clean the house. Tracey and her daughter Susy can clean the house in 4 hours. When they all three work together they can clean the ho

Algebra ->  Rate-of-work-word-problems -> SOLUTION: It takes John and his wife Tracey 3.5 hours to clean the house. Tracey and her daughter Susy can clean the house in 4 hours. When they all three work together they can clean the ho      Log On


   

Question 867516: It takes John and his wife Tracey 3.5 hours to clean the house. Tracey and her daughter Susy can clean the house in 4 hours. When they all three work together they can clean the house in 3 hours. How long does it take Susy to clean the house by herself?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
1/j+1/t=1/3.5,
1/t+1/s=1/4,
1/t+1/j+1/s=1/3
1/t+1/j+1/s=1/3
1/t +1/s=1/4,
1/j=4/12-3/12
1/j=1/12
j=12
1/t+1/j+1/s=1/3
1/t+1/j=1/3.5
1/s=1/3 -1/3.5
1/s=3.5/10.5-3/10.5
1/s=1/21
s=21

1/t+1/s=1/4,
1/t+1/21=1/4
1/t=21/84-4/84=17/84
t=84/17
j = 12, s = 21, t = 84/17
j=12., s=21., t=4.94118