eoje balpyohadaga silsuhaesseoyo.

In this sentence, -다가 means while doing something or in the middle of doing something.

So:

• 발표하다 = to give a presentation
• 발표하다가 = while giving a presentation / in the middle of giving a presentation

The full sentence means that the mistake happened during the presentation.

A very important nuance is that -다가 often connects one action to another event that happens partway through the first action. Here, the speaker was presenting, and then a mistake happened during that process.

발표하다가 is the correct form because -다가 attaches to the verb stem.

• 발표하다 → verb stem: 발표하-
• 발표하- + -다가 → 발표하다가

It only looks like the full dictionary form is being used because verbs ending in 하다 combine very naturally this way.

Why not 발표해다가?
Because -다가 does not attach to the -아/어 form. It attaches directly to the stem.

Why not 발표하면서?
-면서 also means while, but it usually just describes two actions happening at the same time:

• 음악을 들으면서 공부했어요 = I studied while listening to music.

By contrast, -다가 often suggests:

1. an action was in progress, and
2. another event happened during it, often suddenly or unexpectedly.

So 발표하다가 실수했어요 feels very natural for I was giving a presentation, and I made a mistake in the middle of it.

That is exactly what it is.

• 발표 = presentation / announcement
• 하다 = to do

So 발표하다 literally means to do a presentation, which in natural English becomes to give a presentation.

This is very common in Korean. Many verbs are made this way:

• 공부하다 = to study
• 운동하다 = to exercise
• 실수하다 = to make a mistake
• 발표하다 = to give a presentation

So in this sentence, both main verbs are noun + 하다 verbs:

• 발표하다가 = while giving a presentation
• 실수했어요 = made a mistake

Korean often leaves out the subject when it is clear from context.

So 어제 발표하다가 실수했어요 does not explicitly say I or she or they, but in many normal situations it will be understood as:

• I made a mistake while giving a presentation yesterday

If needed, you could add the subject:

• 제가 어제 발표하다가 실수했어요 = I made a mistake while giving a presentation yesterday.
• 민수가 어제 발표하다가 실수했어요 = Min-su made a mistake while giving a presentation yesterday.

But if everyone already knows who is being talked about, Korean usually omits it.

실수했어요 means made a mistake.

Breakdown:

• 실수하다 = to make a mistake
• 실수했어요 = made a mistake / I made a mistake

This is a very common and natural expression in Korean.

It is a little different from 틀렸어요:

• 실수했어요 focuses on making an error, often accidentally, in an action or situation.
• 틀렸어요 often means something was wrong or incorrect, like a wrong answer.

For this sentence, 실수했어요 is the best choice because the speaker is talking about messing up during a presentation.

Great question. The past tense is shown in the main verb, which is 실수했어요.

So the structure is:

• 어제 = yesterday
• 발표하다가 = while giving a presentation
• 실수했어요 = made a mistake

The whole sentence is clearly in the past because the main event, the mistake, happened in the past.

The -다가 part gives the background action and does not need its own past marking here.

If you said 발표했다가, that would usually mean something different, more like:

• after doing the presentation / having presented, then...
• or it can sometimes carry a contrastive nuance depending on context

So 발표하다가 실수했어요 is the natural way to say I made a mistake while presenting.

Yes. In many cases, -다가 suggests that something happened mid-action, often unexpectedly, and sometimes the second event is negative or disruptive.

So 발표하다가 실수했어요 does not just mean two things happened at the same time. It gives the feeling:

• I was presenting,
• and in the middle of that,
• I ended up making a mistake.

This nuance makes it especially good for accidents, interruptions, or sudden changes.

For example:

• 가다가 넘어졌어요 = I fell while walking.
• 숙제하다가 잠들었어요 = I fell asleep while doing homework.
• 말하다가 울었어요 = I started crying while speaking.

So here, -다가 fits very naturally because making a mistake during a presentation is exactly the kind of event it often describes.

Yes, 실수했어요 already shows past tense, but 어제 gives a specific time reference: yesterday.

Without 어제, the sentence would simply mean:

• I made a mistake while giving a presentation

With 어제, it becomes:

• I made a mistake while giving a presentation yesterday

In Korean, it is very common to use both:

• a time word such as 어제, 오늘, 방금
• and a past or present verb ending

So this sentence is completely normal and natural.

실수했어요 is in the polite informal style, often called the -아요/어요 style.

It is polite and very common in everyday conversation.

Compare:

• 실수했어요 = polite, everyday standard
• 실수했습니다 = more formal
• 실수했어 = casual, used with close friends or younger people

So the full sentence 어제 발표하다가 실수했어요 sounds polite and natural in ordinary conversation, such as talking to a teacher, coworker, classmate, or someone you do not speak casually with.