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## Kindergarten

### Course: Kindergarten>Unit 1

Lesson 4: Comparing small numbers

# Comparing numbers on the number line

Sal uses number line to compare numbers less than or equal to 10. Created by Sal Khan.

## Want to join the conversation?

• Can the number line be extended?
• Number lines go on forever, in both directions! If you go to the right, the numbers keep getting bigger. After 100, you have 101, then 102 and so on. Before 0 you have the negative numbers.
• What happen when they use negative number like:
What is greater than -2 ?
a. 2
b. -1
c. 0
d. -3
What will be the answer if this was one of the problems?
• If that was a question the correct answers would be a, b and c.
Since: -2 < -1 < 0 < 2.
• Is greater then always to the right of the number and less then always to the left of the number?
• Yes, assuming that the numbers are increasing from left to right.

Although unconventional, you could draw a number line with the numbers increasing right to left, in which case the greater numbers would be to the left.
• When doing mental math do most of you visualize a number line or use a different technique?
• When doing mental math, I often break the numbers into parts. For example, when I add `82 + 123`, I would break it into parts: `100 + 80 + 20 + 3 + 2`. Sometimes I mentally simplify the equation too; once I break it into parts, I add some of them together, to simplifying it to `100 + 100 + 5`. Once completing the equation, the answer would be `205`.
• why is the greater and less then sign called an aligater
• Because the little angle that points to either side looks like an alligator jaw.
• So does this concept include negative numbers?
• Well you actually do negative numbers on the number line but it is not covered in early math.
• Can number lines be seperated by other numbers besides one?
• Yes, they can be separated by 2, or any other number. You just have to have the same difference between each one.
• is there something special about stopping at 100 or can you keep going? As long as you are consistent you can keep going. o i almost forget can there be -infinity?
• No, there is nothing special about 100, it's just the first 3-Digit Numeral. This helps young kids keep track of their numbers. Also, for your second question, yes, but keep in mind, infinity is a concept. It is not a number, which is why you can't do anything with it. But, +Infinity is the "greatest" number, and -Infinity is the "smallest" number. The reason they are in quotes is because there is no such thing as the greatest or smallest number, you can always add one more. Hope that helps!

Sincerely,
Aanand Kainth
• Can the number line go to 100 or can the number line go farther than 100?