Properties and Patterns of Addition and Subtraction

The commutative property of addition says that the order of the numbers in an addition problem does not change the answer. 8 + 4 = 12 and 4 + 8 = 12

Addition and subtraction sentences of three numbers can be written if the sum of two numbers is the third number. 3 + 2 = 5; 2 + 3 = 5; 5 – 2 = 3; 5 – 3 = 2. This group of sentences is called a fact family

The sum of any number and 0 is that number. This is called identity property of addition. For example, 17 + 0 = 17

When three numbers are added, it makes no difference which two are added first. This is known as associative property of addition. For example, 2 + (4 + 3) = (2 + 4) + 3

A pattern is a series of numbers or figures that follows a rule

Multiples of 10, 100, and 1000 can be added by using a pattern
For example, add 200 and 600
First, add:
2 ones + 6 ones = 8 ones
2 + 6 = 8
Now use this answer to add:
2 tens + 6 tens = 8 tens
20 + 60 = 80
2 hundreds + 6 hundreds = 8 hundreds
200 + 600 = 800

A pattern is a series of numbers or figures that follows a rule

Multiples of 10, 100, and 1000 can be subtracted by using a pattern
For example, subtract 200 from 600
First, find the difference:
6 ones - 2 ones = 4 ones
6 - 2 = 4
Now use this answer to find difference:
6 tens - 2 tens = 4 tens
60 - 20 = 40
6 hundreds - 2 hundreds = 4 hundreds
600 - 200 = 400