# In How Many Days, B Alone Can Do it? If

A works twice as fast as B. If both of them can together finish a work in 4 days, then in how many days, B alone can do it?

- 12
- 16
- 11
- 15

**Answer: (1) 12**

**Explanation:-**

Let the B can finish the work = X days

Then , B can work in a day = 1/ X

A can finish the work = X/2

Then, A can work in a day = 2/ X

A and B can together work in a day = 1 / X + 2 / X

= (1 + 2 ) /X

= 3 / X

Then, A and B can together finish a work = X / 3 = 4

X = 4 x 3

X = 12

Then, B can alone finish the work = 12

Hence, the answer is (1) 12.