4.2.1 An Everyday Problem

Let’s suppose you purchased four large pepperoni pizzas that cost $15.99 each, and you want to split the total cost among six people evenly. To determine how much each person needs to pay, both addition and division will be used. Fortunately, you’ve brought your calculator along, so you type it in as follows: . You push the “=” button or enter and the result is$50.635. Your friends aren’t going to be too pleased about that! What went wrong?

Well, you soon realize that what your calculator has done is to calculate , because it follows the order of operations, PEMDAS. Your calculator has divided only the last $15.99, not the total, by six. What you need it to do is calculate the total first by putting it into parentheses: . Now you can divide (remember, P comes before D in PEMDAS). Then, you get each. Each person owes$10.66, not more than \$50. Phew—much relief all around!

So you can see now how important it is to get the correct order for calculations.

4.2 Order of Operations

4.2.2 Calculator Exploration: Understanding the Order of Operations