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This is a problem from TOMATO Problem number 2, useful for ISI and CMI entrance exam based on Men and Job.

**Problem:**

If m men can do a job in d days, then the number of days in which m+r men can do the job is

(A) d+r; (B) $\frac{d}{m} (m+r)$ ; (C) $\frac {d}{m+r}$ ; (D) $\frac {md}{m+r}$;

**Discussion:**

If m men can do a job in d days,

Then m men does $\frac {1}{d}$ job in 1 day

Then 1 man does $\frac {1}{md}$ job in 1 day

Then m+r men does $\frac {m+r}{md}$ job in 1 day

Then m+r men does 1 job $\frac {md}{m+r}$ days.

Hence answer is $\frac {md}{m+r}$ days (D)

**What is this topic:**Arithmetic**What are some of the associated concepts:**Unitary Method**Where can learn these topics:**Cheenta I.S.I. & C.M.I. course, discusses these topics in the ‘Arithmetic’ module.**Book Suggestions:**Arithmetic by K.C. Nag

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