Rabbi can do 1/3 of a work in 5 days. In how many days will he complete the work?

Question: Rabbi can do 1/3 of a work in 5 days. In how many days will he complete the work?

Solution:
Rabbi can do 1/3 of the work in 5 days.
he will complete the work in = 5 × 3 days
= 15 days