Varun and Karun can do a piece of work in 18 days and 27 days respectively. Karun starts the work and Varun joined him after some days. The total work is completed in 15 days from the beginning. After how many days did Varun joined with Karun?
1
7 days
2
8 days
3
9 days
4
6 days
5
None of these