Question

please ans this question.

Answer 1

fraction of work done in one by A,B andC is

1/40,1/50 and 1/80

In first 7days ,fraction of work completed by A is 7/40

eighth day ,B and C are joining A then fraction of work completed on 8th day will be 1/40+1/50+1/80=23/400

so total fraction of work done after 8days

7/40+23/400=93/400

now whole work will be done in (400/93) ×5=2000/93 days.

47

=21 ------ days.

93