P and Q can harvest a field in 5 and 7 days respectively.after P has worked for 3 days, he is joined by Q.in how many more days will the work be completed?

P`s one day work =

Q`s one day work =

Since P worked alone for 3 days,

work completed by P =

Work left =

Now, Q also joined P.

So, work done by them in one day = P`s one day work + Q`s one day work

=

So, of work is completed in 1 day

so, of work will be completed in

Hence, the work will be completed on the second day when they start working together.

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