Other uses of the たら conditional

Question

Passing a verb to its past tense conjugation and adding ら makes the sentence a condition, right? Like

暇だったら、遊びに行くよ - If I'm free, I will go to play.

But in the ももたろう tale the たら form is used differently in the sentence:

ある日、 おばあさん が 川 で せんたく を して いたら、
ももがながれて きました

The translation I found states that "one day, WHILE the old lady was at the river doing the laundry a peach came floating by" so my question is: Is this translation any good? Can the たら conditional be used to relate two actions taking place at the same time? Can it be interpreted as 'while'?

Further ahead there's a sentence that says:

ひろって たべたら、
なんとも おいしくて ほっぺた が おちそう。

Which translates as: She picked it up and ate it and, it was so delicious as if to make her cheeks fall.

So what is the role of たら here?

Thank you very much.

Answer 1

Your first understanding is correct. The other usages you give are also correct and I would consider them good translations. While it is a 'conditional' it has a broader meaning than just 'if'. Like in the latter examples it is also used to indicate an event that occurred unexpectedly as a result of another action, or linked to it in some way. In such cases there's an implication that without the first action, the second one wouldn't have occurred and it was not anticipated that the second event would occur and often when used like this it is translated as 'when' or 'while'.

For example:「一人で歩いてたら、怖い男に話しかけられた。」ー”A scary guy approached me when I was walking by myself.”

Here you can see there are two things - walking and being approached by someone. It is implied that they would not have been approached had they not been walking and it's as a result of being out walking by themselves that they were approached and this was not expected to have happened.

In the last example you give たら is indicating that they were not expecting it to be so delicious their cheeks fell off but when they ate it, they discovered that was the case.

So as you can see in all these examples B is always 'conditional' on A.

Answer 2

「・・・たら」 is used in different ways of (1) conditional as in the case of 「暇だったら、遊びに行く」 and (2) conjugate as in the cases of 「洗濯 を して いたら、桃が流れてきた」 and 「拾って食べたら、美味しかった」.

Here are some examples:

[Conditional]

• もっと勉強したら、東大に入れる - If you study harder, you can get into Tokyo University.

• もし癌だったら、大変だ - If it’s cancer, it’s a big trouble.

• 結婚式を終わったら、ハワイ旅行に出かける - If we go through a wedding ceremony, we’ll go to Hawaii.

[Conjugate]

• 運転していたら、前の車にぶつかった - As I was driving a car, I bumped into a car running ahead of me.

• 電車に乗ったら、偶然席が空いていた - When I got into the train, there was an unexpectedly unoccupied seat.

• 難しい哲学の本を読んでいたら、頭痛がした - As I was reading a difficult book of philosophy, I felt a headache.