Question

A can do a piece of work in 5 days . B can do the same work in 15 days .how long will it take if both A and B work together?

Answer 1

Explanations :- A's 1 day work = 1/5

B’s 1 day work = 1/15

So taken together A and B, both of them complete work in 1 day.

(A + B)'s 1 day work = 1/5+1/15

= 20/75

=4/15

= 1/3.75


So, Number of days they take to finish work together = 1/3.75 = 3.75 days or 4 days (round off).

Answer 2

A can do a work =in 5 d
he can do in 1 day =1/5 of that work
B can do that work =in 15 d
B can do in 1 d=1/15 of that work
A & B can do in 1 d=1/5+1/15
. =5/15+1/15=6/15 of that wok
they will do the all work= 1÷6/15
. =15/6 days
=2d&12h