Question

pls answer this frds...​

Answer 1

Answer:  30 days.

Step-by-step explanation:

A can do it in 80 days.

Therefore , A's 1 day work=1/80

 and so A's 10 day work=(1/80)*10=1/8.

So, a has done 1/8 of the work .

Work left to do= 1-(1/8)=(8-1)/8=7/8.

ATP,

       B does 7/8 work in 42 days.

       So , B does 1 work in 42*8/7 days=48 days

  so B's 1 day work=1/48.

total 1 day work of A + B =    1/80   +      1/48

                                        =           (3+5)/240

                                        =           8/240

                                        =            1/30

So A's+B's 1 day work =1/30

so they take 30 days to do the work together.