YOU SAID:

This is so stupid! How am I supposed to know this?!?

INTO JAPANESE

なんてバカなの！どうして私がそんなことを知る必要があるの？！？

BACK INTO ENGLISH

How stupid! Why would I need to know that?!?

INTO JAPANESE

バカだね！なんでそんなことを知る必要があるの？！？

BACK INTO ENGLISH

That's stupid! Why do you need to know that?!?

INTO JAPANESE

それはバカだ！なぜそれを知る必要があるのか？

BACK INTO ENGLISH

That's stupid! Why do you need to know that?

INTO JAPANESE

それはバカだ！なぜそれを知る必要があるの？

BACK INTO ENGLISH

That's stupid! Why do you need to know that?