Question

A construction crew builds 2 floors of a skyscraper every 10 days. How log will it take for the crew to build 15 floors on the skyscraper

Answer 1

2 floors are built every 10 days.

1 floor can be built in 10/2 days.

15 floors can be built in (10/2) * 15 =  5 * 15 = 75 days.