Questions & Answers about Quantos livros você quer comprar hoje?
Quantos agrees in gender and number with the noun livros (books).
- livro = masculine singular → matching question word: quanto livro? (how much book? – normally you’d use the plural in real speech)
- livros = masculine plural → matching question word: quantos livros? (how many books?)
Forms of quanto:
- quanto – masculine singular (quanto dinheiro?)
- quanta – feminine singular (quanta água?)
- quantos – masculine plural (quantos livros?)
- quantas – feminine plural (quantas pessoas?)
So you use quantos because livros is masculine and plural.
In this sentence, quantos means how many (countable items).
General rule:
- Use quanto / quanta / quantos / quantas with nouns.
- Countable → how many: quantos livros (how many books), quantas maçãs (how many apples)
- Uncountable → how much: quanto dinheiro (how much money), quanta água (how much water)
English splits the idea into how much vs how many, but Portuguese always uses some form of quanto, changed for gender and number.