Percentages are proportions used represent the size of one quantity compared with another. You can use percentages to represent sales prices, such as 20 percent off, success rates, such as getting 86 percent of the questions correct, or parts of a whole, such as the portion of total company sales a salesperson generated. Percentages also help you make a meaningful comparison when two different data sets have different totals. For example, you can compare how often two batters get a hit using percentages, even though the batters may have different numbers of atbats and hits. To calculate a percentage with a calculator, you need to know the two quantities you are comparing.

Enter the portion you are converting to a percentage in the calculator. If you are calculating a test grade, you would enter the number of correct answers. For example, if the student got 43 questions right, you would enter "43."

Push the division button on the calculator. The division button is usually represented by "÷."

Enter the second quantity, often the total amount, in the calculator. If you were calculating a test grade, you would total the number of questions on the test. For example, if you there were a total of 50 question on the test, you would enter "50."

Push the equals button, usually represented by the "=" sign on the calculator, to determine the proportion. For example, if a student got 43 out of 50 questions correct, your answer would be .86.

Push the multiplication button, usually represented by "×," on the calculator.

Enter "100" and push the equals button to convert the proportion to a percentage. For example, 0.86 would become "86," meaning 43 out of 50 is equivalent to 86 percent.
Tips & Warnings
 Make sure you divide the portion you are focusing on by the total, not the other way around, or your calculations will be incorrect.
References
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