Варка риса занимает больше времени, чем варка макарон.

Because both of them depend on the noun варка and answer the question варка чего? = the boiling/cooking of what?

That means they go in the genitive case:

• рис → риса
• макароны → макарон

So:

• варка риса = the cooking/boiling of rice
• варка макарон = the cooking/boiling of pasta

This is very common in Russian with verbal nouns:

• чтение книги = reading of a book / reading a book
• приготовление ужина = preparation of dinner
• строительство дома = construction of a house

The basic form is макароны, but this noun is normally used only in the plural in Russian. It behaves like a plural-only noun.

Its forms include:

• nominative: макароны
• genitive: макарон

Since after варка we need the genitive, we get варка макарон.

So even though English often says pasta as a mass noun, Russian commonly uses plural макароны.

Варка is a noun formed from the verb варить, which means to boil / to cook by boiling.

So варка риса literally means:

• the boiling of rice
• or more naturally in English, cooking rice

This word is a bit more technical, formal, or process-focused than everyday speech. It sounds like you are talking about the activity itself as a process.

In everyday Russian, people might more naturally say:

• Рис варится дольше, чем макароны.
  = Rice takes longer to cook than pasta.

Not exactly.

• варка = cooking by boiling specifically
• готовка = cooking in a broad, everyday sense
• приготовление = preparation, often more general and a bit more formal

So in this sentence, варка is used because both rice and pasta are typically boiled.

Compare:

• варка риса = boiling/cooking rice
• приготовление риса = preparing rice, more general
• готовка is less likely in this exact structure for this meaning

Because the subject is варка риса, and that whole phrase is grammatically singular.

The main subject is not риса. The subject is the noun варка:

• Варка риса = singular subject
• therefore занимает = singular verb

The second part, чем варка макарон, is just the comparison part: than cooking pasta.

So the structure is:

• [Варка риса] занимает больше времени
• чем [варка макарон]

This is a very common Russian pattern.

• больше = more
• времени = time, in the genitive case

So занимает больше времени literally means takes more time.

Russian often uses больше + genitive after words meaning more / less:

• больше времени = more time
• меньше денег = less money
• больше работы = more work

This is one of the most natural ways to express duration in Russian.

Yes. A very natural alternative is:

• Варка риса длится дольше, чем варка макарон.
• Рис варится дольше, чем макароны.

These all express roughly the same idea.

The differences are small:

• занимает больше времени = takes more time
• длится дольше = lasts longer
• варится дольше = cooks/boils longer

In everyday conversation, many speakers would prefer something simpler like:

• Рис варится дольше, чем макароны.

Чем means than in comparisons.

So:

• больше времени, чем ... = more time than ...
• дольше, чем ... = longer than ...

Here it introduces the second item being compared:

• Варка риса занимает больше времени, чем варка макарон.
• Cooking rice takes more time than cooking pasta.

Without чем, the comparison would be incomplete.

Yes, often it can.

Russian often omits repeated words when the meaning is clear. So you may also hear:

• Варка риса занимает больше времени, чем макарон.

However, many learners find the full version easier to understand:

• ...чем варка макарон

Keeping the second варка makes the structure very explicit and balanced.

Yes, it is grammatical and understandable, but it sounds somewhat formal, neutral, or expository, as if from a textbook, recipe discussion, or general statement about cooking processes.

In more everyday speech, a Russian speaker would often say:

• Рис варится дольше, чем макароны.
• Рис готовится дольше, чем макароны.

So the original sentence is fine, but it is more focused on the process than on the food itself.

Yes, Russian word order is flexible, though some versions sound more neutral than others.

The original sentence:

• Варка риса занимает больше времени, чем варка макарон.

is perfectly natural and neutral.

You could also say:

• Больше времени занимает варка риса, чем варка макарон.

But that sounds more marked or stylistically heavier.

For learners, the original order is the best one to remember because it is clear:

1. subject: Варка риса
2. verb: занимает
3. object/measure: больше времени
4. comparison: чем варка макарон

Because the noun варка comes from варить, which specifically refers to boiling or cooking in water.

That fits both foods here:

• rice is typically boiled
• pasta is typically boiled

If Russian wanted a more general idea of preparing food, it could use something broader like приготовление. But варка is more precise for this context.