Question

A is twice as efficient as b and can complete a job 30days before

b.in how much they can complete the job together?

Answer 1

(15×45)/15+45=( 15+45)/60=45/4= 11¹/⁴

Answer 2

If A does a job in 30 days, B will take 60 days to complete the same job. (Just for the sake of A completing it 30 days before B)

Job completed by A in 1 day=1/30

Job completed by B in 1 day=1/60

Job completed by them in 1 day together=2+1/60=3/60=1/20

let x be the days in which they complete the job

So,

x/20=1

x=20

So, while A was takng 30 days to complete a job and B was taking 60 days to complete the same job, together they can do it in 20 days.