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Have you ever heard the mnemonic: PEMDAS or “Please Excuse My Dear Aunt Sally?”

What does it stand for? P: Parentheses E: Exponents M: Multiplication D: Division A: Addition S: Subtraction Across the world, we have decided to use this order to solve equations with many operations. If you do it in the wrong order, you will get a different answer.

4 Which side of the road do we drive on? The right side.

5 What would happen if you didn’t drive on the right side?

6 What if everyone agreed to drive on the left side, what would happen? In many countries, people drive on the left, rather than the right.

7 Order of Operations Section 1.3

(Please write this down) Simplify problems in this Order: P: parentheses ( ) E: exponents Base exponent M/D: multiplication and division from left to right A/S: addition and subtraction from left to right

Example of Left/Right Issue The first step: DIVIDE the 6 by 2. Then you MULTIPLY the answer by 3.

Equations + Variables = Algebra A letter used in math is called a “variable.” (More on this soon) Replace the letter with a given number: What is x + y if x = 2 and y = 3? 2 + 3= 5

Replace the letters with numbers, and solve. Example: if a = 2 and b = 7 4(2) 3 - (7 - 3) 4(8) - (4)

12 Fractions and PEMDAS Do the top and bottom of the fraction separately. Imagine parentheses around the top and bottom.

13 Practice Problems You may work with one other person, or by yourself. (No groups larger than two.) Make sure you write your name(s). Please write on a separate piece of paper. You may turn in one paper per group. Please feel free to ask for help.

14 Practice 1-3 EXAMPLE EXERCISES Choose one problem from “Example 1” Choose four problems from “Example 2” Choose four problems from “Example 3” Choose four problem from “Example 4” Why do we multiply the tax by the total and then add it to the original price? Why don’t we find the tax for each object? WARNING: This is the hardest one.

Homework: Textbook pg 17-18, 1-23 odds