Order of Operations Lesson - Addition and Subtraction
Fill in the missing numbers:If addition is the only operation, the ORDER in which you do the operations doesn't matter. For example: 13 + 7 + 2 = ?
If you add 13 and 7 first, you get _____
Then when you add 2, you get a final answer of ______
On the other hand, if you add 7 and 2 first, you get _____
Then when you add 13, you get a final answer of ______
The answers are the same - with ADDITION the order doesn't matter.
With subtraction, however, the order DOES matter. For example:13 - 7 - 2 = ?
If you do 13 - 7 first, you get _____
Then when you subtract 2 from that, you get a final answer of ______
HOWEVER, if you do 7 - 2 first, you get _____
Then if you subtract that from 13, you get a final answer of ______
The answers are different. It depends which subtraction you do first.
With SUBTRACTION the order DOES matter.
What about a problem with both addition and subtraction?
Work through this example to see for yourself: 13 - 7 + 2 = ?
13 - 7 = _____
and then when you add 2 you get a final answer of ______
Doing it in a different order: 7 + 2 = _____
and when you subtract that from 13 the final answer is ______
When there is both addition and subtraction, the order DOES make a difference.
To avoid confusion, the left-to-right Order of Operations rule has been adopted:
For addition and subtraction, work from left to right.
Apply the left-to-right Order of Operations rule to the two previous expressions.
13 - 7 - 2 = 6 - 2 = _____
13 - 7 + 2 = _____ + 2 = _____