A and B can do a work in 10 days and 20 days respectively. They started the work together but A left the work 2 days before the completion of the work. In how many days was the work completed?

8

A left the work before 2 days of completion of work.

A's 2 days work = 2 × 2 = 4 unit

Let us consider , Total work = 20 = 4 = 24 unit

Time taken by both A and B to complete the work = \(\frac{24}{ 2 + 1 }\)

= \(\frac{24}{ 3 }\)

=  8 days

The correct answer is Option (3) → 8