# A takes 6 days less than the time taken by B to finish a piece of work. If both A and B together can finish it in 4 days, how many days will B take to finish the work?

We will use the concept of work done to solve this question.

## Answer: 12 days

Let's assume B takes x days to finish the work. We get the quadratic equation in terms of x and we will solve the equation.

## Explanation:

Suppose B alone takes x days to finish the work. Then A alone can finish it in (x−6) days

Now A's one day's work + B's one day's work = 1/x + 1/(x - 6) and (A + B)'s one day's work = 1/4

1/x + 1/(x - 6) = 1/4

⇒(x − 6) + x / x(x - 6) = 1/4

⇒ (2x - 6)/(x^{2 }- 6x) = 1/4

⇒8x − 24 = x^{2 }− 6x

⇒x^{2} − 14x + 24 = 0

⇒x^{2} − 12x − 2x + 24 = 0

⇒x = 12 or x = 2, but x cannot be less than 6.

So, x = 12