Question

Two Men can do a piece of work in 6 hour and 4 hour respectively.After the first has worked for two hour,He joined by other. By when we should the work be completed.

Answer 1

Time taken by first worker to do the work = 6 hours

Time taken by second worker to do the work = 4 hours

in one hour first can do=1/6 part of the work

in two hours he can do= 1/3 part of work

remaining work=2/3 part of work

both can do the work in = 1/(6+4)/(6*4)

                                        =12/5 hrs

full work is done in 12/5 hrs

2/3 part of work is done in =2/3*12/5 hrs

                                           =1.6hour

total time=1.6+2

               =3.6 hour