В супермаркете я взял тележку и положил яблоки на весы, чтобы узнать цену.

Because в супермаркете means in the supermarket, describing location, not motion.

• в + Prepositional case = location: в супермаркете
• в + Accusative case = motion into somewhere: в супермаркет

Compare:

• Я был в супермаркете. = I was in the supermarket.
• Я пошёл в супермаркет. = I went to the supermarket.

So in your sentence, the speaker is already there, so в супермаркете is correct.

These are past-tense, masculine singular verb forms.

• взял = took
• положил = put

The subject is я, but Russian past tense agrees in gender and number, not person. Since the speaker is understood to be male here, the forms are masculine:

• masculine: взял, положил
• feminine: взяла, положила

So a woman would say:

В супермаркете я взяла тележку и положила яблоки на весы, чтобы узнать цену.

Because the sentence describes completed, one-time actions in sequence:

1. he took a cart
2. he put the apples on the scales
3. he wanted to find out the price

Russian often uses perfective verbs for completed actions in a story.

Aspect pairs here are:

• брать / взять = to take
• класть / положить = to put

Why perfective here?

• взял = he took it successfully, as a completed action
• положил = he placed them, completed action

If you used imperfective, it would sound more like process, habit, or background action.

Because тележку is the direct object of взял, so it is in the accusative case.

The dictionary form is:

• тележка = cart / trolley

For a feminine noun ending in -а, the accusative singular usually changes to -у:

• тележка → тележку

So:

• я взял тележку = I took a cart

It is accusative plural, but for inanimate plural nouns, the accusative form is usually the same as the nominative.

Dictionary form:

• singular: яблоко = apple
• plural nominative: яблоки
• plural accusative: яблоки (same form, because the noun is inanimate)

So in:

положил яблоки = put the apples

яблоки is the direct object, so it is accusative, even though it looks like nominative plural.

Because на весы shows motion onto the scales.

Russian uses:

• на + Accusative = movement onto a surface
• на + Prepositional = location on a surface

So:

• положил яблоки на весы = put the apples onto the scales
• яблоки лежат на весах = the apples are lying on the scales

That is the same pattern as:

• положить книгу на стол = put a book onto the table
• книга лежит на столе = the book is lying on the table

Because весы is one of those Russian nouns that normally exists only in the plural.

It means scales.

This is similar to some English words that are often treated as plural in form, such as scales, scissors, or pants.

So although it refers to one object, the Russian word is plural:

• весы
• на весы
• на весах

There is no normal singular form used for ordinary weighing scales in this meaning.

This means in order to find out the price.

чтобы introduces a purpose:

• чтобы = so that / in order to

Here the subject is the same person throughout, so Russian commonly uses:

• чтобы + infinitive

So:

• чтобы узнать цену = in order to find out the price

If the subject were different, Russian would usually use a finite verb instead. For example:

• Я положил яблоки на весы, чтобы продавец узнал цену. = I put the apples on the scales so that the shop assistant could find out the price.

Because узнать means to find out / to learn, while знать means to know.

• знать цену = to know the price
• узнать цену = to find out the price

In the sentence, the speaker does not know the price yet. He puts the apples on the scales in order to discover it, so узнать is exactly the right verb.

Also, узнать is perfective, which fits the idea of getting the information as a completed result.

Because цену is the direct object of узнать, so it is in the accusative singular.

Dictionary form:

• цена = price

Accusative singular:

• цена → цену

So:

• узнать цену = to find out the price

This is the same pattern as other feminine nouns ending in -а:

• машина → машину
• газета → газету

Yes, Russian often can omit subject pronouns when the meaning is clear. So you could say:

В супермаркете взял тележку и положил яблоки на весы, чтобы узнать цену.

But including я is also perfectly natural. It can do a few things:

• make the sentence clearer
• add a little emphasis
• sound more natural in a narrative, depending on context

So both are possible. The version with я is not wrong or strange.

No, Russian word order is flexible. The sentence given is natural, but other orders are also possible depending on emphasis.

Neutral version:

В супермаркете я взял тележку и положил яблоки на весы, чтобы узнать цену.

If you want to emphasize the location, starting with В супермаркете works well. If you want to emphasize the subject, you might say:

Я в супермаркете взял тележку...

Russian word order often reflects emphasis, topic, and style more than strict grammar.

Yes. Russian has no articles like a/an or the, so яблоки can mean:

• apples
• the apples

Context tells you which is meant.

In this sentence, English would probably naturally say the apples, because the speaker is talking about specific apples they are buying. But Russian does not need a separate word for that.

In this context, yes.

тележка can mean a small cart or trolley in general, but in a supermarket it naturally means a shopping cart.

Depending on region and context, learners may also hear корзина for a shopping basket. So:

• тележка = shopping cart / trolley
• корзина = basket

In your sentence, взял тележку means I took a shopping cart.