42 binders can bind 1400 books in 15 days. How many binders will be required. bind 800 books in 20 days?

Question: 42 binders can bind 1400 books in 15 days. How many binders will be required to bind 800 books in 20 days?

Solution:
In 15 days 1400 books can be bound by 42 binders
In 1 day 1 book can be bound by (42 × 15)/1400 binders
In 20 days 800 books can be bound by (42 × 15 × 800)/(1400 × 20) binders
= 18 binders