Last year, there were a total of 100 + 50 = <<100+50=150>>150 books in the library.

The library purchased 50 x 3 = <<50*3=150>>150 books this year.

Therefore, the library now has a total of 150 + 150 = <<150+150=300>>300 books.

# Answer

300
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Last year, the school library purchased 50 new books. This year, it purchased 3 times as many books. If the library had 100 books before it purchased new books last year, how many books are in the library now?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
300
Last year, the school library purchased 50 new books. This year, it purchased 3 times as many books. If the library had 100 books before it purchased new books last year, how many books are in the library now?
train