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3-digit numbers

Definitions


  • We can group 10 ones into 1 ten:
    = \(10\) ones \(= 1\) ten =
  • We can also group 10 tens into 1 hundred:
    = \(10\) tens \(= 1\) hundred =
  • To count how many hundreds, tens, and ones there are, we can make a table:
    Hundreds Tens Ones
    2 4 3
    The table tells us we have 2 hundreds, 4 tens, and 3 ones, which we can write in positional notation as 243.

Definition Digits
A digit is a single symbol representing a number.
zero 0
one 1
two 2
three 3
four 4
five 5
six 6
seven 7
eight 8
nine 9
Definition Base 10 system
In the base 10-system, the place of a digit in a number determines its value. We can represent a number:
  • with digits: $$243$$
  • in expanded form: $$\begin{aligned}[t] 2\text{ hundreds }&+& 4\text{ tens }&+& 3\text{ ones }\\200 &+&40&+&3 \\\end{aligned}$$
  • with words:
    two hundred forty-three
  • in a table:
    Hundreds Tens Ones
    2 4 3
  • with cubes:
Zero acts as a placeholder to show there is nothing in a certain position. For example, in 20, zero shows there are no ones.

On the Number Line


  • A number line shows numbers like 0, 1, 2, 3, and so on in order.
  • Let’s make counting easier by counting by tens on our number line. Now we jump 10 at a time: 0, 10, 20, 30.

Definition Number Line
A number line is a line that shows numbers in order. Moving right adds by same number.