Question

A can do a job in 6 days while A and B can do it together in 2 days . how many days will be taken by B to do the job alone​

Answer 1

Solution :

A can do a job in 6 days

So, work done by A in 1 day = 1/6

A and B can do it on 2 days

So, work done by A and B in 1 day = 1/2

We know that

Work done by B = Work done by A and B - Work done by A

= 1/2 - 1/6

Taking LCM

= (3 - 1)/6

= 2/6

= 1/3

i.e Work done by B = 1/3

⇒ B can do it in 3 days.

Hence, B alone can do the job in 3 days.

Answer 2

Given :---

• A can do a work in = 6 days .
• A+B can do the same job in = 2 days .

To Find :----

• Time taken by B to do same work alone ?

Solution :-----

LCM of 6 and 2 = 6 = Total work .

efficiency of A = 6/6 = 1 unit / day

efficiency of A+B = 6/2 = 3 unit / day.

so, efficiency of B = (A+B) - A = 3-1 = 2 unit/day .

time taken by B to complete whole work = 6/2 = 3 days .

Hence , B will take 3 days alone to do whole work ..