イタリアの人口は、日本の人口の約半分だ。
The population of Italy is about half as large as that of Japan.

遊び半分に学校へ来るな。
Don't come to school to lark around.

面白半分なら来ないで欲しい。
If you're doing it in fun, I'd rather you didn't come.

はい、お兄ちゃん、半分こ。
Here, bro, halfsies.