Welcome to addition and subtraction within 20! This fundamental math skill involves calculations where all numbers stay between 0 and 20. Let's see an example: 8 plus 6 equals 14. All numbers in this calculation are within our range.
One effective strategy for addition within 20 is counting on. Start with the larger number and count up by the smaller number. For example, to solve 7 plus 3, start at 7 and count up: 8, 9, 10. This method is faster than counting from 1.
For subtraction within 20, we can use the counting back strategy. Start with the larger number and count backwards by the amount being subtracted. For example, to solve 15 minus 4, start at 15 and count back: 14, 13, 12, 11. The answer is 11.
The making 10 strategy is very useful for addition within 20. Break one number into parts to make 10 first, then add the remaining. For 8 plus 5, we take 2 from the 5 to make 8 plus 2 equals 10, then add the remaining 3 to get 13.
Let's practice with some examples! 12 plus 6 equals 18. 17 minus 5 equals 12. 9 plus 7 equals 16. 20 minus 8 equals 12. Great job! Remember to use counting on for addition, counting back for subtraction, and the making 10 strategy. Practice makes perfect!