Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 一个教室里有45个孩子。其中三分之一是女孩。教室里有多少个男孩？


### Response:
 女孩占班级的三分之一，所以班级里有45 / 3 = <<45/3=15>>15个女孩。
所以教室里有45 - 15 = <<45-15=30>>30个男孩。