SOLUTION: Working together, Bob, Sally, and Harry can dig a hole in 3.5 hours. Working alone, Harry can do it in 7 hours. Bob can do it 3/4 hours fasters than Sally. How long will it take fo

Question 686116: Working together, Bob, Sally, and Harry can dig a hole in 3.5 hours. Working alone, Harry can do it in 7 hours. Bob can do it 3/4 hours fasters than Sally. How long will it take for Sally to dig a hole alone?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Add their rates of working to get their time
working together
= Bob's time to dig hole in hours working alone
= Sally's time to dig hole in hours working alone
= Harry's time to dig hole in hours working alone
-------------
given:
(1)
(2)
(3)
-----------------
Substitute (2) and (3) into (1)
(1)
(1)
Multiply both sides by
(1)
(1)
(1)
Solve using quadratic equation

Sally can dig the hole alone in
14 hrs and 23 min
check:
(1)

(1)
(1)
(1)
I think error is due to rounding off
OK

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