The ratio of boarders to day students at a school was originally 5 to 12. However, after a number of new boarders join the initial 330 boarders, the ratio changed to 1 to 2. If no boarders became day students and vice versa, and no students left the school, how many new boarders joined the school?  Choose the correct choice from the following choices: A) 48 B) 66 C) 72 D) 80 E) 84

Rationale: let x be the number of new boarders . the ratio changed from 5 : 12 up to 1 : 2 = 6 : 12 . 330 / ( 330 + x ) = 5 / 6 x = 66 the answer is b .
Answer: B