SOLUTION: PIPE A CAN FILL A POOL IN 12 HOURS. AFTER IT HAS BEEN USED FOR 4.5 HOURS. PIPE B IS ALSO USED; AND THE POOL IS FILLED IS ANOTHER 4.5 HOURS. HOW LONG WOULD IT TAKE FOR PIPE B TO FI

Algebra ->  Rate-of-work-word-problems -> SOLUTION: PIPE A CAN FILL A POOL IN 12 HOURS. AFTER IT HAS BEEN USED FOR 4.5 HOURS. PIPE B IS ALSO USED; AND THE POOL IS FILLED IS ANOTHER 4.5 HOURS. HOW LONG WOULD IT TAKE FOR PIPE B TO FI      Log On


   

Question 162357: PIPE A CAN FILL A POOL IN 12 HOURS. AFTER IT HAS BEEN USED FOR 4.5 HOURS.
PIPE B IS ALSO USED; AND THE POOL IS FILLED IS ANOTHER 4.5 HOURS. HOW LONG WOULD IT TAKE FOR PIPE B TO FILL THE POOL BY ITSELF.
PIPE A RATE 1/12
PIPE B RATE = Z
PIPE A RUNS FOR T WHICH IS 4.5 + 4.5 = 9
PIPE B RUNS T - 4.5

T*R = w
T(1/12) + T-4.5(1/Z)=1
9(1/12) + 9-4.5(1/Z)=1
9/12 + 4.5/Z =1
4.5/Z = 1-9/12
4.5/Z = 3/12
4.5/Z = 1/4
Z = 18 HRS
WHERE DID GO WRONG?

Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
you managed to "stumble" onto the correct answer

you defined Z as the rate __ "PIPE B RATE = Z"
__ but then used 1/Z in your calculations

"T*R = w"
"T(1/12) + T-4.5(1/Z)=1"
"9(1/12) + 9-4.5(1/Z)=1"