oh.. it seem like a kind of quizs for native korean kids. the counting word for 젓가락 is '쌍' 젓가락 한 쌍 두 쌍 세 쌍 but we hardly use this word. we say simply '젓가락 한 개 두개 세 개' here is a fun story about this happening to me. i was in a chicken store to take out a fried chicken and there was a couple who ordered some chikens. The cleark asked to them 'how many chopstics do you need' and then the man of the couple answered "We need 여섯개" After a while he corrected his words into "세개" and then the girl of the couple started laughing and said "you idiot! you thought 젓가락 한 쌍 is actually 두 짝 and just multiplied 3 by 2" and then all the people in the store laughed. By the way, a half of 젓가락 한 쌍 is called 젓가락 한 짝