Sam can do a job in 4 days

Lisa can do a job in 6 days

Tom can do a job in 2 days

How long can Sam Lisa and Tom complete the job?

.8 1.09 1.23 1.65 1.97

I cannot remember how to start this problem can somebody please help me

Thank you

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- Aug 26th 2008, 05:07 PM #1

- Joined
- Feb 2007
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- 32

- Aug 26th 2008, 05:13 PM #2
hmm...

Sam does 1/4 of a job per day (job per day is like miles per hour, if you want to think of it that way)

Lisa has a speed of 1/6 of a job per day

Tom has a speed of 1/2 of a job per day

So, they complete the job $\displaystyle n$ amount of days later...

$\displaystyle \frac{1}{4}n+\frac{1}{6}n+\frac{1}{2}n=1$

Let's solve for n, first we multiply both sides by 12 to get:

$\displaystyle 3n+2n+6n=12$

Then add:

$\displaystyle 11n=12$

Then divide:

$\displaystyle n=\frac{12}{11}=1.0909090909090909090909...$

So they can finish the job in $\displaystyle \approx 1.09 \text{ days}$