Discussion :: Time and Work
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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?
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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
Hence, total time taken = (6 + 4) days = 10 days.
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