### 1.1 Order of Operations & Formulas

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• Math Help

Calculators use a variety of symbols to represent the mathematical operations. For example, some calculators have the symbol (±) rather than (−) to enter a negative number.

Calculators also vary on how they interpret "order of operations." There are three basic types:

1. PEMDAS:  Use the conventional order of operations that is accepted in math.

2. Operation Activated:  Each operation activates the equal key.

3. RPN:  Reverse Polish Notation is used by some technical calculators.

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• Checkpoint Solution

Using the standard order of operations, you need to add the numbers in parentheses before dividing. So, (d) is a correct way to find the average.

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Try confirming this by estimating the answer and then trying both ways with your calculator. The average of 50, 62, and 73 is about 60. Some calculators give \$136.33 for (c) while all calculators give \$61.67 for (d). The keystrokes for (d) are closest to the estimate, so (d) is a correct way to find the average.

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