The ratio of boarders to day students at a school was originally 2 to 5. However, after a number of new boarders join the initial 60 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 answers:  A) 12  B) 15  C) 20  D) 24  E) 30
Let x be the number of new boarders.   The ratio changed from 2:5 = 4:10 up to 1:2 = 5:10.   60 / (60+x) = 4/5   x = 15   The answer is 15.
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The ratio of boarders to day students at a school was originally 2 to 5. However, after a number of new boarders join the initial 60 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?