Type 1 workers can do three times the work of Type 2 workers. Twelve Type 1 workers can complete a task in 10 days. How many days would it have taken 4 Type 1 and 8 Type 2 workers to complete the same task?

Type 1 Worker-

12 Type 1 workers can complete the work in 10 days.

So, 1 Type 1 workers can complete the work in 12x10 days i.e. 120 days.

Type 1 workers 1 day's work= 1/120.

4 Type 1 workers 1 day's work= 4/120= 1/30.

Since, the Type 1 is 3 times efficient than Type 2. So,

Type 2 Worker-

1 Type 2 workers can complete the work in 12x10x3 days i.e. 360 days.

Type 2 workers 1 day's work= 1/360.

8 Type 2 workers 1 day's work= 8/360= 1/45.

So, 1 day's work of Type 1 and Type 2 workers= 1/30+1/45= 1/18.

So, total time taken to complete the work= 18 days.

Therefore, Option D is correct.