说明
从惯用法上看,在动词 cut, break, divide 或 fold 等动词后,使用 in half 也是正确的,而且是一种较常见的用法,甚至在数学教科书中也是如此:
Fold the bill in half and then in half again. (Essentials of Mathematics, 1977) 把这张纸币对折一次, 然后再对折一次。
再看下面的托福题：
When a bacterium becomes too large, it splits in half and forms two new bacteria, each with its own cell wall and protoplasm. (TOEFL) 当细菌变得很大时，它就分裂成两半，生成两个新的细菌，每个都有自己的细胞壁和细胞质。