Ten-something, twenty-something: mười mấy, hai mươi mấy, mấy chục

You know mấy as "how many?", and as "a few" in a statement. After a round number it means "and a few more": mười mấy is ten-something, anywhere from eleven to nineteen. Em gái tôi mới mười mấy tuổi. My little sister is only in her teens.

It works after any ten: hai mươi mấy (twenty-something), ba mươi mấy (thirty-something). It's the easy way to give an age without being exact: Ảnh chắc hai mươi mấy tuổi. He's probably in his twenties (in Hà Nội, anh ấy). In quick speech you'll also hear the shorter hai mấy, ba mấy.

Hundreds work the same way, and you'll hear this a lot with prices: hai trăm mấy ngàn, two hundred and something thousand đồng (in Hà Nội, nghìn).

At the front, before chục (ten), trăm or ngàn, mấy means "several": mấy chục người (dozens of people), mấy trăm người (hundreds of people). Mấy chục is vaguer than vài chục (a few dozen), which keeps the number small.

Khoảng gives a figure that could fall either side: khoảng hai mươi is about twenty. Hai mươi mấy is always more than twenty and less than thirty.