Learn Italian: Abbiamo cento grammi di pasta, ne cucino cinquanta. - We have a hundred grams of pasta, I am cooking fifty.

In this sentence, ne replaces the phrase grammi di pasta. When you state a quantity like cinquanta (fifty) in Italian but don't repeat the noun, you must use ne to mean 'of it' or 'of them'. So ne cucino cinquanta literally means 'I cook fifty of them'.

Why is ne placed before the verb cucino?

Like other small pronouns you have learned (such as lo, la, or mi), ne is a clitic pronoun and must be placed immediately before the conjugated verb. Even though the quantity cinquanta comes after the verb, the pronoun ne still has to go before it.

Why do we just say cento instead of un cento for 'a hundred'?

In Italian, you never use the word un (a/one) before the exact numbers cento (100) or mille (1,000). While English says 'a hundred', Italian simply says cento.

Why do we use the preposition di before pasta?