You know we must?

[jplato]

OK, so I understand that 공부해야 돼 is the form for "must study", but how would you construct "you know we must study"? Can you combine 야 돼 with 잖아, like 야 돼잖아 or something?

[holdfast]

you could say 공부 해야 되잖아 or 공부 해야 하잖아 i think.

i usually say 공부 해야 지 which has the same sort of meaning in this context (i think).

but you might want to wait for a better answer, as i am no expert. ^^

[Chris1]

She's right. If you're trying to get a study buddy to stop goofing off:

"야 우리 공부해야 되잖아"

will work fine.

However, if you're passing him down the hall before your study time, and you want to confirm/remind with him of your plans:

우리 오늘 공부하기로 한 게 맞지?
We're still on for studying today, right?

우리 오늘 공부해야 되는 거 알지?
You know we gotta study today, right?