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A can do a piece of work in 4 days. B can do it in 20 days. With the help of C, they finish the same work in 2 days. In how many days can C alone do t
Question

A can do a piece of work in 4 days. B can do it in 20 days. With the help of C, they finish the same work in 2 days. In how many days can C alone do the same work?


A.


B.

7

C.

5

D.

4

Correct option is C

Given:

- A completes the work in 4 days 

- B completes the work in 20 days  

Solution: 

Total work =  LCM of 4 , 20 = 20 unit 

Efficiency of A = 20/4 = 5

Efficiency of B = 20/20 = 1 

With the help of C they can complete 2 days 

Efficiency of A + B + C  = 202\frac{20}{2} = 10 unit 

Efficiency of C = 10 - 5 -1 = 4 unit/day 

C alone complete tte work  = 204=5\frac{20}{4} = 5  days ​

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