If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Class 1>Unit 2

Lesson 1: Counting numbers from 1 to 20

# Teens as sums with 10

Sal looks at the 1 in each teen number and thinks about what it really means.  Created by Sal Khan.

## Want to join the conversation?

• Why does it say 11 and 12 are teen numbers? They don't have teen in it's name.
• Teen numbers are numbers in the range of 11-19.
• so what is a teen number?
• A teen number is a number between 11 and 20
• Not all 2 digit numbers are teens. I thought that teen numbers only go from 13-19? For example if I was 13 I would be a teen right? But if I was twelve I wouldn't be a teen. Im confuzled.
• Don't base your idea of teen numbers off of age. (That can be very confusing!) The teen numbers actually go from 11-19. Just because the number does not have the word "teen" in it, does not rule that particular number out. Hope that helps.
• Is there a way to say zero in Roman numerals?
• There is no roman numeral, but the Latin word "Nulla" (none) was used instead.
• why does it have to be ten + another number to get that number? example: 10 + 3 = 13
• Because this is the lesson about adding ten to numbers. 10 is equal to 1 ten, and 3 is 3. Then, add one ten and a three, you get thirteen (13).
• At why does he say Lurie and what does it mean?
• Sal is referring to the mathematicician Jacob Lurie, panelist who talks about that concept.