는지(요) especially at the end of the sentence can be used in various meanings. 1) when you have a doubt about something : 그게 맞는지.= (I’m not sure) if that’s right. 그게 맞는지요 = Is that right? (if you add 요 at the end it becomes a question.) 그녀가 나를 좋아하는지. = (I’m not sure) if she likes me 그녀가 저를 좋아하는지요? = Does she like me? 2) to check facts in the past : 저녁은 먹었는지. = I wonder if you had dinner. 저녁은 드셨는지요? = Did you have dinner? 거기까지 가는데 오래 걸리지는 않았는지. = I wonder if it took too long to get there. 거기까지 가는데 오래 걸리지는 않았는지요? = Did it take long to get there? 3) to ask whether she/he did something ~했는지 안했는지 = Whether you did it or not 니가 먹었는지 안먹었는지 = Whether you ate it or not