Question 880397
A can do a piece of work in 9 days, B in 12 days and C in 18 days.
 A & B work for 3 days after which C replaces B.
 How long must A & C work together to finish the job?
:
let t = days A & C must work together to finish the job
Let the completed job = 1
:
A shared work equation
{{{((t+3))/9}}} + {{{3/12}}} + {{{t/18}}} = 1
multiply equatin by 36, cancel the denominators, you then have:
4(t+3) + 3(3) + 2t = 36
4t + 12 + 9 + 2t = 36
6t + 21 = 36
6t = 36 - 21
6t = 15
t = 15/6
t = 2.5 days A & C working together
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