Time and Work - Arithmetic Aptitude Questions and Answers

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Discussion :: Time and Work

X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?

6 days

10 days

15 days

20 days

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Answer : Option B

Explanation :

Work done by X in 4 days =[ $\frac { 1 } { 20 } *4]$ = $\frac { 1 } {5}$

Remaining work =[1- $\frac { 1 } {5}$ ]= $\frac { 4 } {5}$

(X + Y)'s 1 day's work =[ $\frac { 1 } { 20 }$ + $\frac { 1 } { 12 }$ ]= $\frac { 8} {60}$ = $\frac { 2 } {15}$

Now, $\frac { 2 } {15}$ work is done by X and Y in 1 day

So, $\frac { 4 } {5}$ work will be done by X and Y in[ $\frac { 15 } {2} *$ $\frac { 4 } {5}$ ]=6days