Amit alone can complete a piece of work in 15 days and Balbir alone can do the same work in 10 days. If Amit alone works for 3 days after which Balbir joins him, then the remaining work will be finished in how many days?

Correct option is A

Given:

Amit can complete a piece of work in 15 days.

Balbir can complete the same work in 10 days.

Formula Used:

work done = number of days $$\times$$ efficiency

Solution:

let total work  = 30 units 

we take work done  is 40 because of 40 is the LCM of 15,10 .

efficiency of Amit= total work done \  time in which he do it 

=30\15 

                       =2 unit

efficiency of Balbir = total work done \  time in which he do it 

                       =30\10

                    =3

Amit complete the work in 3 days = number of days $$\times$$​ efficiency

                                                            =3 $$\times$$ 2

                                                           =6 unit

work remaining = 30 -6 = 24 units

so Amit and Balbir  complete the all work in = total work \ efficiency 

                                                           = 24\5

                                                       =4$$\frac{4}{5}$$ days​