Question

A and b working separately can do a piece of work in 5 and 7 days respectively.if they work for a day alternatively with a beginning,in how many days will the work be completed

Answer 1

A complete the whole work in 5 days that means he completes (1/5) amount of work in single day. Similarly B completes (1/7) amount of work in single day.

Now let's assume that A started first and did (1/5) amount of work and on next day B did (1/7) amount of work. So tatal work completed in 2 days when both are working alternatively will be = ((1/5)+(1/7)) = (12/35)

So, if the same thing repeats for 2 times then amount of work completed = 2x(12/35) = 24/35
That means after 4 days (24/35) amount of work is completed.

now on 5th day A will complete ( 1/5) amount of work so total work done = (24/35)+(1/5) = (31/35)

and on 6th day B will the remaining (4/35) amount of work.

So the answer is 6 days.

Answer 2

Hey user here is your answer

Image attached

Hope it helps