Daily Expression
Ａ:	山口さんがこの前ゴルフコンペで優勝してパソコンをもらったんだって！
Ｂ:	ええ、本当？　でも、彼パソコンの使いかた知ってるの？
Ａ:	いいや、彼は機械にはまったく弱いから猫に小判だろうね。
Romaji:
Ａ:	Yamaguchi san ga konomae gorufu-kompe de yuushooshite pasokon o morattandatte!
Ｂ:	Ee, hontoo? Demo, kare pasokon no tsukaikata shitteruno?
Ａ:	Iiya, kare wa kikai ni mattaku yowai kara neko ni koban daroone.
Translation:
Ａ:	Did you hear that Mr. Yamaguchi won a PC as a first prize in a golf tournament?
Ｂ:	Did he? But does he know how to use it?
Ａ:	He has no idea about machinery.　It is just “Pearls cast before swine”!

猫に小判 ／ neko ni koban:
“Neko”, a cat would not know that value if she was given “Koban”, a Japanese ancient gold coin. In other words it is useless to give somebody a very valuable thing if this person don’t know what it is. A similar English expression is “Pearls cast before swine".
Another example
Ａ:	この間の中国旅行で素敵なお皿を買ってきたの。あなたと川口さんにあげようと思って….。どう？
Ｂ:	わあ、素敵ねえ！ ありがとう。でも…川口さんは陶磁器なんかには全然興味がないから、猫に小判だと思うよ。それよりも私に２枚ちょうだい！
Romaji:
Ａ:	Konoaida no chuugoku ryokoo de sutekina osara o katte kita no.　Anata to kawaguchi san ni ageyoo to omotte…　Doo?
Ｂ:	Waa, suteki ne!　Arigato.　Demo…　kawaguchi san wa toojiki nanka niwa zenzen kyoomi ga naikara, neko ni koban dato omou yo. Soreyorimo watashi ni nimai choodai!
Translation:
Ａ:	I bought some nice plates when I went to China the other day. There are two of them, and I'm going to give one to you and the other one to Mrs Kawaguchi. Here it is.　How do you like it?
Ｂ:	Terrific!　Thank you.　It will be worthless to give a plate to Mrs Kawaguchi, because she is not interested in China at all. Why don’t you give me the two plates instead?