If you use these simple formulas for work and time problems asked in CAT and other competitive exams, you can not only save time but will also get correct results.

- The following are the formulas that should be memorised

1. If X can finish a work in “a” time and Y can finish the same work in “b” time then both of them together can finish that work in

(**a x b)/ (a+b)** time.

2. If X can finish a work in “a” time and X & Y together can finish the same work in T time then Y can finish that work in

**(a xT)/(a-T)** time.

3. If X can finish a work in “a” time and Y in “b” time and Z in “c” time then all of them working together will finish the work in

**(a x b x c)/ (a x b + b x c + a x c)** time

4. If X can finish a work in “a” time and Y in “b” time and X, Y & Z together in T time then

- Z can finish that work alone in
**(a x b x T)/ (a x b- T x a- T x b)** - Y+Z can finish in
**(T x a)/(a-T);**and - X+Z can finish in
**(T x c)/(b-T)**

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