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Question 508350: Mary, sue and bill work at a motel. If each worked alone, it would take mary 10 hours, sue 8 hours and bill 12 hours. One day Mary came to work early and she had cleaned for 2 hours when Sue and bill arrived all three finished the job. How long did they take to finish?
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! Mary, sue and bill work at a motel. If each worked alone, it would take mary 10 hours, sue 8 hours and bill 12 hours. One day Mary came to work early and she had cleaned for 2 hours when Sue and bill arrived all three finished the job. How long did they take to finish?
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Mary's work rate=1/10
Sue's work rate=1/8
Bill's work rate=1/12
..
let x=hours all three took to finish the job
work done = hours on the job*work rate
(x+2)(1/10)+x/8+x/12=100%=1
LCD:10*8*12=960
96(x+2)+120x+80x=960
96x+192+120x+80x=960
296x=960-192
296x=960-192=768
x=768/296=2.59 hrs (rounded)
ans:
Hours all three took to finish the job=2.59 (rounded)
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