Azhar is 4 times as good a workman as Balaraj and therefore is able to finish a job in 45 days less than Balaraj. Working together, they can do it in:

Ratio of times taken by Azhar and Balaraj = 1 : 4

The time difference is (4 - 1) 3 days while Balaraj take 4 days and Azhar takes 1 day.

If difference of time is 3 days, Balaraj takes 4 days.

If difference of time is 45 days, Balaraj takes = $$\frac{4}{3} \times 45 = 60$$ days

So, Azhar takes 15 days

Azhar's 1 day's work = $$\frac{1}{15}$$

Balaraj's 1 day's work = $$\frac{1}{60}$$

(Azhar + Balaraj)'s 1 day's work together = $$\frac{1}{15} + \frac{1}{60} = \frac{4+1}{60} = \frac{1}{12}$$

$$\therefore$$ Azhar and Balaraj together can do the work in = 12 days

=> Ans - (D)