A sum of money is sufficient to pay A's wages for 20 days and B's wages for 30 days. The same money is sufficient to pay the wages of both for?
Choices:
A) 12 days
B) 15 days
C) 20 days
D) 18 days
E) 22 days

Rationale: "let the total money be $ x a ' s 1 day work = $ x / 20 b ' s 1 day work = $ x / 30 a + b 1 day work = $ x / 12 money is sufficient to pay the wages of both for 12 days answer is a"
Answer: A