[email protected] wrote:Mac can finish a job in M days and Jack can finish the same job in J days. After working together for T days, Mac left and Jack alone worked to complete the remaining work in R days. If Mac and Jack completed an equal amount of work, how many days would have it taken Jack to complete the entire job working alone?
(1) M=20 days
(2) R=10 days
Mac and Jack complete an equal amount of work.
In other words, each produces 1/2 the job.
Since Mac works for a total of T days with Jack, Mac's time to produce 1/2 the job = T.
Since Jack works for T days with Mac and for R days alone, Jack's time to produce 1/2 the job = T + R.
Thus, Jack's time to produce the whole job = 2(T+R).
Question stem rephrased: What is the value of 2(T+R)?
Statement 1: M=20
Since Mac takes 20 days to produce the whole job, he takes 10 days to produce 1/2 the job.
Since he produces 1/2 the job in the T days that he works with Jack, T = 10 days.
No way to determine the value of R.
INSUFFICIENT.
Statement 2: R=10
No way to determine the value of T.
INSUFFICIENT.
Statements combined:
Jack's time to produce the whole job = 2(T+R) = 2(10+10) = 40 days.
SUFFICIENT.
The correct answer is
C.
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