Learn Hardcore Japanese: sensei ni meeruadoresu wo kikareta toki, sugu ni kotaeraremasita. - When the teacher asked for my email address, I could answer right away.

Active: 先生が私にメールアドレスを聞いた。
– 先生が = teacher is the subject/doer.
Passive: 私は先生にメールアドレスを聞かれた。
– 先生に = “by the teacher” (agent of the passive).

So に here is not “to the teacher”, but “by the teacher”.

Where is “I” in this sentence? Why isn’t 私 written?

Japanese frequently omits subjects when they’re clear from context.

The “full” version of the sentence would be:

私は先生にメールアドレスを聞かれたとき、すぐに答えられました。
→ When I was asked my email address by my teacher, I was able to answer immediately.

Here, 私は is obvious:

Talking about being asked your email address.
Talking about your ability to answer (答えられました is in polite form, so it’s likely the speaker talking about themselves).

Because of that, Japanese drops 私は and just says:

先生にメールアドレスを聞かれたとき、すぐに答えられました。

Native speakers rely on context rather than always stating “I”.

Why is it 聞かれたとき and not 聞かれましたとき?

Two points:

The verb before とき must be in the plain form (dictionary or plain-past), not in ます-form.
So:
- ✅ 聞くとき / 聞いたとき / 聞かれるとき / 聞かれたとき
- ❌ 聞きますとき / 聞きましたとき
It’s normal in Japanese to have:
- subordinate clause (before とき) in plain form
- main clause in polite form

So the pattern:

聞かれたとき、すぐに答えられました。

is the standard way to say this politely. Having 聞かれましたとき would be ungrammatical.

What’s the difference between 聞かれたとき and 聞かれるとき?

The verb form before とき affects the timing:

聞かれたとき (past)
→ when I was asked / at the time (after) I had been asked.
The asking is seen as a completed event at that moment.
聞かれるとき (non-past)
→ when I am asked / when I get asked (whenever that happens).
This usually expresses a general situation, habit, or future event.

In your sentence, we’re talking about one specific time in the past, so 聞かれたとき is appropriate:

When I was (actually) asked my email address, I could answer right away.

Why 答えられました instead of just 答えました?

答えられました is the potential form (polite past):

Dictionary form: 答えられる = can answer / be able to answer
Polite past: 答えられました = was able to answer / could answer

So the nuance is:

すぐに答えました。
→ I answered immediately. (just states the fact)
すぐに答えられました。
→ I was able to answer immediately. (emphasizes that it was easy / within my ability / I knew it)

Because it’s about your ability to recall your own email address on the spot, 答えられました sounds natural.

Is 答えられました passive or potential? How can you tell?

For ichidan verbs like 答える, 〜られる can be both:

passive: 答えられる = to be answered
potential: 答えられる = can answer

So you need context.

In this sentence:

先生にメールアドレスを聞かれたとき already uses 聞かれる as a passive.
With 答える, the usual pattern is X に答える (answer X), not *X を答える.
There is no agent with に after 答えられました (no “by someone”).

So 答えられました here clearly means:

I was able to answer (the teacher/the question).

A true passive would look like:

質問はすぐに答えられました。
→ The question was answered quickly.

But that wouldn’t fit the context of “I answered (my teacher)”. So here it’s potential.

Why do we have すぐに instead of just すぐ? Is there a difference?

Both are correct:

すぐ答えられました。
すぐに答えられました。

すぐ is an adverb meaning immediately / right away.
Many adverbs can optionally take に to sound a bit more “adverb-like” or slightly more formal/smoothed.

Nuance:

すぐ: a little more casual/spoken.
すぐに: slightly more neutral/polished, and flows well in writing.

In everyday speech you will hear both all the time; the meaning is the same.

Why is it メールアドレスを聞かれたとき and not メールアドレスを答えられました? Shouldn’t we “answer the email address”?

Two separate verbs are used differently:

聞く
- 〜を聞く = ask for / hear ~
  → メールアドレスを聞く = ask (someone) for their email address
答える
- 〜に答える = answer ~
  → 先生に答える = answer the teacher
  → 質問に答える = answer the question

So in your sentence:

メールアドレスを belongs to 聞かれた
→ was asked for my email address.
For 答えられました, the thing you’re answering is understood but omitted:
- (先生に / 質問に) すぐに答えられました。
  → I was able to answer (the teacher / the question) immediately.

We normally don’t say メールアドレスを答える. Instead:

先生にメールアドレスを言う / 教える = tell the teacher your email address
質問に答える = answer the question

So the pattern in the sentence is natural Japanese usage.

Could I say 先生がメールアドレスを聞いたとき、すぐに答えられました instead? Does it change the nuance?

Yes, you can say:

先生がメールアドレスを聞いたとき、すぐに答えられました。

This is grammatically correct and understandable.

Nuance difference:

先生がメールアドレスを聞いたとき…
– more neutral; focuses on what the teacher did (the teacher asked).
先生にメールアドレスを聞かれたとき…
– keeps the focus on the speaker as the one something happened to (I was asked by the teacher).

In situations where you’re telling a story about what you experienced, the passive version often feels a bit more natural in Japanese.