Time and Work on Arithmetic Aptitude related Questions and Answers

Question :   A can do a certain work in 25 days which B alone can do in 20 days. A stared the work and was joined by B after 10 days. The work was completed in 1. 18 2/3 days 2. 16 2/3 days 3. 14 1/3 days 4. 15 1/3 days Answer :   2 - 16 2/3 days