|Objective(s): By the end of this lesson the student will be able to:
the order of operations to solve math equations.
Pre Class Assignment: Completion of Algebra Lesson 3
In the first
learned that numbers and variables form sentences, or algebraic
"expressions." When you take information from a sentence and turn it
into a mathematical expression, it is called "translating." In another
lesson, you learned that when you write algebraic expressions, use +,
-, and = signs; and for division, use / , the same way you know that
when you see a fraction, it means to divide the top number by the
bottom number. Then, for multiplication, we learned to write the
expression with no symbol or sign between them (such as 3a), with an X
, or using parentheses. The parenthesis is especially useful in longer
problems such as (3y)(4-2x).
But what if there
are no parentheses or brackets? How do you know which to do first? Add,
divide, multiply? Which one?
When there are no
other indications as to which computation to do first, mathematicians
follow The Order of Operations rule. Multiply, Divide, Add,
A good way to
remember the Order of Operations is to think about My Dear Aunt Sally.
The M is for multiply, the D in Dear is for Divide, the A is for Add,
and the S in Sally is for subtract.
HINT: If the problem has only multiplication and division, then work
from left to
HINT: If the problem has only subtraction and addition, then work from
left to right.
Let's Get Started:
13 - 2 X 5
If I just do the
math from left to right, I would say 13 - 2 = 11. Then 11 times 5 = 55.
But the Order of
Operations tells me to multiply first! So, 2 X 5 = 10. Then, I subtract
10 from 13 and get 3.
You can see that
which order you choose makes a BIG difference in the answer! That's why
it's important to follow the Order of Operations.
Now it's time for
you to try a few.
Assignment(s) including Answer key:
1. 10 - 4 + 3
2. 10 + 4 X 2
3. (5 X 4) -15 + 2
4. 12 - 2(3 + 1)
5. 18 + 2(3)
6. (12 - 2)(3 + 4)
7. 4 X 3 + 5
8. 24 - 6 +2
9. 24 - 6 X 2
10. 36/9 - 2
For Answer Key, Click Here
Pre-Requisite To: Basic Algebra - Lesson
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