geollero chaeksang miteul dakkeun da-eume bisjaruwa sseurebatgireul beranda-e dueosseo.

-로 marks the tool, means, or instrument used to do something.

So 걸레로 닦다 means to wipe/clean with a rag.

A useful contrast:

• 걸레로 닦았어 = I wiped it with a rag
• 걸레를 닦았어 = I cleaned/wiped the rag

Here, 걸레 is not the thing being cleaned; it is the thing used to clean.

책상 밑 means under the desk or the area underneath the desk.

• 책상 = desk
• 밑 = bottom, underside, underneath

In this kind of phrase, 밑 acts like a noun meaning the lower/under area of something. So 책상 밑 is literally the desk’s underside/under-area.

Because with 닦다 you usually mark the thing being wiped/cleaned as the direct object, so it takes -을/를.

So:

• 책상 밑을 닦다 = to wipe/clean under the desk / the area under the desk

If you used -에, it would sound unnatural with 닦다 in this sentence.

A helpful comparison:

• 책상 밑을 닦았어 = I cleaned the area under the desk
• 책상 밑에서 닦았어 = I cleaned something while being under the desk / in the location under the desk

So -을 is used because 책상 밑 is what got cleaned.

Because 밑 is often treated as a dependent noun in expressions like this.

So Korean normally writes:

• 책상 밑
• 침대 밑
• 의자 밑

This is similar to how Korean often separates words like 위, 아래, 앞, 뒤, 옆, 안 when they function as nouns referring to position.

닦은 다음에 means after wiping or after having wiped.

It is made from:

• 닦다 = to wipe
• 닦은 = the past adnominal form of the verb
• 다음에 = after, next

So the pattern is:

Verb-(으)ㄴ 다음에 = after doing Verb

Examples:

• 먹은 다음에 = after eating
• 끝난 다음에 = after it ended
• 닦은 다음에 = after wiping

This pattern connects two actions in sequence.

Not in this sentence.

On its own, 다음에 can mean next time:

• 다음에 보자 = See you next time / See you later

But in the grammar pattern V-(으)ㄴ 다음에, it means after doing something:

• 닦은 다음에 = after wiping

So the meaning depends on the structure around it.

Because the two nouns are joined into one coordinated object phrase, and the object marker is attached at the end of the whole phrase.

So:

• 빗자루와 쓰레받기를 = the broom and dustpan
  • object marker

This is very normal in Korean.

You can think of it like:

• [빗자루와 쓰레받기]를 두었어
• I put [the broom and dustpan]

Both nouns are objects, but Korean does not need to put -를 on each one.

Yes.

These all can mean and:

• 빗자루와 쓰레받기
• 빗자루하고 쓰레받기
• 빗자루랑 쓰레받기

The difference is mostly style/register:

• 와/과 = a bit more neutral or written/formal-feeling
• 하고 = very common in speech
• (이)랑 = casual/conversational

In this sentence, 와 sounds completely natural.

Because 에 marks the place where something is put/left.

With verbs like 두다, 놓다, 붙이다, 넣다, Korean normally uses 에 for the destination or resulting location:

• 책상 위에 두다 = put it on the desk
• 방에 두다 = leave it in the room
• 베란다에 두다 = leave it on/in the veranda

By contrast, 에서 usually marks the place where an action happens:

• 베란다에서 청소했어 = I cleaned on the veranda

So here, the broom and dustpan ended up at the veranda, which is why 에 is used.

It is the past form of 두다, but it often carries the nuance of putting something somewhere and leaving it there.

So 베란다에 두었어 means something like:

• I put it on/in the veranda
• I left it on/in the veranda

That left there in that state feeling is very natural with 두다.

Also, in everyday speech, 두었어 is very often contracted to 뒀어.

So you may hear:

• 베란다에 두었어
• 베란다에 뒀어

Both are natural; 뒀어 is more conversational.

They are very similar here, and in many everyday situations they can overlap.

• 두다 often feels like put/leave
• 놓다 often feels like put down/place

In this sentence, both could work depending on nuance:

• 베란다에 두었어
• 베란다에 놓았어

But 두다 is especially common when the idea is that something was placed somewhere and remained there.

두었어 is casual, non-polite speech.

It would be used with:

• close friends
• younger people
• someone you speak casually with

Polite versions:

• 두었어요 = polite
• 뒀어요 = polite, contracted and common in speech

So the sentence ends in a casual style.

It is omitted, which is very common in Korean.

Korean often leaves out the subject when it is clear from context. So this sentence could mean:

• I wiped under the desk and then left the broom and dustpan on the veranda
• He/She/They did that

The subject does not have to be stated if the listener already knows who is being talked about.

Yes. Very common alternatives are:

• 닦고 나서
• 닦은 후에

All of these mean roughly after wiping.

Nuance:

• 닦고 나서 = very common in everyday speech
• 닦은 다음에 = also very common and clear
• 닦은 후에 = a bit more formal/written

So this sentence could also naturally be said with 닦고 나서.