YOU SAID:

You must have been living under a rock for twenty years to have not heard of that!

INTO JAPANESE

そんなことを聞いたことがないなんて、20年間も世間知らずに暮らしていたに違いない！

BACK INTO ENGLISH

I must have been living in ignorance for 20 years to have never heard of such a thing!

INTO JAPANESE

そんなことを一度も聞いたことがないなんて、20年間も無知のまま生きてきたに違いない！

BACK INTO ENGLISH

I must have lived twenty years in ignorance to have never heard of such a thing!

INTO JAPANESE

そんなことを一度も聞いたことがないなんて、私は20年間も無知のまま生きてきたに違いありません。

BACK INTO ENGLISH

I must have lived 20 years of ignorance to have never heard of such a thing.

INTO JAPANESE

そんなことを一度も聞いたことがないなんて、私は20年間も無知のまま生きてきたに違いない。

BACK INTO ENGLISH

I must have lived 20 years in ignorance to have never heard of such a thing.

INTO JAPANESE

そんなことを一度も聞いたことがないなんて、私は20年間も無知のまま生きてきたに違いありません。

BACK INTO ENGLISH

I must have lived 20 years of ignorance to have never heard of such a thing.

INTO JAPANESE

そんなことを一度も聞いたことがないなんて、私は20年間も無知のまま生きてきたに違いない。

BACK INTO ENGLISH

I must have lived 20 years in ignorance to have never heard of such a thing.