Learning Subtraction Within 20
What You Already Know: You can subtract numbers up to 10! Now we will learn to subtract bigger numbers up to 20.
Group 1: Small Numbers (0–9)
These are examples you already know how to count. We count objects and subtract the extra ones.
Eight apples, three crossed out, five left
Nine balls, four crossed out, five left
Examples:
- \(8 - 3 = 5\)
- \(9 - 4 = 5\)
- \(7 - 2 = 5\)
Group 2: Teen Numbers (10–19)
A teen number can be represented as \(10 +\) ones. This makes subtraction easier.
Sixteen is ten and six.
We removed three ones, we get thirteen
Example: \(16 = 10 + 6\). We subtract three ones: \(16 - 3 = 13\).