Subtraction within 20 means taking away one number from another, where the starting number (the minuend) is 20 or less. This helps children understand how to find what is left or the difference between two numbers. Subtraction within 20 strengthens mental math skills and builds a foundation for solving real-life problems.

Key strategies for subtraction within 20:

• Counting back: Start at the larger number and count backward by the smaller number.
• Using number bonds: Recognize pairs of numbers and their relationships to simplify subtraction.
• Relating to addition: Think about what number can be added to the smaller number to reach the larger number.

Examples:

Example 1:
Problem: 15 - 7
Solution: Start at 15 and count back 7: 14, 13, 12, 11, 10, 9, 8.
Answer: 8.

Example 2:
Problem: 12 - 9
Solution: Think of addition: "What number can I add to 9 to get 12?" The answer is 3 because 9 + 3 = 12.
Answer: 3.

By practicing subtraction within 20, children develop fluency in working with smaller numbers and build confidence for tackling more complex subtraction problems.

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