Position is value
Once you pass nine, a single digit is not enough. In base ten, each step left is worth ten times the place to its right.
In 27:
- 2 sits in the tens place → 2 × 10 = 20
- 7 sits in the ones place → 7 × 1 = 7
Together: 20 + 7 = 27.
Check yourself
In the number 45, what does the digit 4 represent?
4 is in the tens place, so it contributes 40.
Number lines
A number line lays quantities out in order from left (smaller) to right (larger). Equal gaps mean equal steps.
To place 30 between 0 and 100, put it about three-tenths of the way along — because 30 is 30% of 100.
Check yourself
On a number line from 0 to 100 with even spacing, 50 sits exactly halfway.
50 is the midpoint of 0 and 100.
Check yourself
How many ones are in three tens?
Example: 30 · integer
3 × 10 = 30 ones.
Check yourself
What number has 4 tens and 8 ones?
4×10 + 8 = 48.