## Percents

• Why should I bother learning this?
The concept of percent is one of the most widely used mathematical concepts in everyday living. Percents are used in finding the interest paid on loans and earned on bank accounts, in computing tips left after a meal or for a hotel room, in computing taxes on meals, hotels, and sales, in computing discounts, and in many more applications. An understanding of percent will be very valuable to your students when they become adults and buy expensive items such as automobiles and homes.

• Why do I multiply by 100 when changing a decimal to a percent?
There are several things you can do to a number and not change its value. You can add or subtract zero or you can multiply or divide by one. When we change a decimal to a percent, we are actually multiplying by one! The percent sign means to divide by 100, so multiplying 0.23 by 100 to get 23 and affixing the percent sign actually divides the number by 100. So, changing 0.23 to 23% really changes how the number 0.23 looks but keeps it equivalent to itself.

• How can something be more than 100%?
Many things can't be more than 100%, but some can be. For example, you can't have a shirt made of 125% cotton, since the total of all elements in the shirt has to equal 100%. Similarly, you couldn't eat 130% of the apples, since all the apples together would equal 100%. However, you can increase the amount of something more than 100%. For example, if you had a business and its profits were \$50,000.00 one year and the profits increased to \$75, 000.00 the next year, the profits for the second year would be equal to 150% of the profits from the first year.

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