15 binders can bind 1400 books in 21 days. How many binders will be required to bind 1600 books in 20 days?
Select:  A) 14  B) 18  C) 24  D) 28  E) none of these

Rationale: "binders books days 15 1400 21 x 1600 20 x / 15 = ( 1600 / 1400 ) * ( 21 / 20 ) = > x = 18 answer : b"
Answer: B