American money has two parts. The big part is the dollar, and the small part is the cent. One hundred cents make one dollar, and the sign for a dollar is $.
Dollars and cents
dollar /ˈdɑː.lər/ — ten dollars
cent /sɛnt/ — fifty cents
Try it: Amina: How much is the shirt? - Lars: Twelve ___ and ninety cents. (dollars / cents / cards) Answer: dollars — The word cents is already there for the ninety, and in one price the same money word is never there twice. The twelve is twelve dollars, and a card is not a price at all.
How much is it?
To ask the price of one thing, say How much is it? You write the answer $4.50, and you say it four fifty or four dollars fifty.
How much is it? — How much is it? Four fifty.
Try it: Lars: ___ Camila: Twenty dollars. Lars is at the watch table with Camila. (How much is it? / How old are you? / How are you?) Answer: How much is it? — Twenty dollars is a price, and a price is the answer to How much is it?How old are you? is a question about Camila, not about the watch.
Cheap and expensive
A small price is cheap, and a big price is expensive. The same thing can be cheap in one store and expensive in another store.
cheap /tʃiːp/ — a cheap T-shirt
expensive /ɪkˈspɛn.sɪv/ — an expensive bag
Try it: Ira: I have thirty dollars. - Maya: This jacket is ninety dollars. - Ira: Oh! It is very ___ for me. (expensive / cheap / new) Answer: expensive — Thirty dollars is not enough for a ninety-dollar jacket, so for Ira it is expensive. Her "Oh!" is not a happy word about a price, and new is not about money at all.
Paying by card
You can pay in two ways. You can pay with dollars and cents in your hand, or you can pay by card.
card /kɑːrd/ — pay by card
Try it: Yasmin: That is nine dollars. - Diego: My wallet is empty today. I pay by ___. (card / cent / price) Answer: card — With an empty wallet, the way to pay is by card. A cent is money in your hand, and Diego has no money in his hand today. A price is a number, not a way to pay.