Question

P and Q can do a piece of work in 12 days and 15 days respectively.p started the work alone then ,after 3 days Q joined him till the work was completed.how long did the work last?​

Answer 1

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In 1- day both together A and B can do = 1/12+1/16 = (4+3)/48= 7/48 -part of the work.

Therefore x/12 + (9-x)7/48 = 1

Upon solving we get 4x + 63–7x= 48

= 3x= 15;

So x= 5

So if “Q” joins after 5- days with“B” the work will be completed in 9- days.