⁦How to Calculate Percentages

ByAgkidzone Staff

Updated: Oct 14, 2024

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Most kids start learning about percentages in fifth or sixth grade. They’re introduced to percentages as parts of a hundred—for instance, 100% means the whole thing, and 50% is half of that, or 50 out of 100. While this basic idea is easy to grasp, figuring out percentages of other numbers can sometimes be tricky. However, understanding percentages is super important for everyday tasks like shopping, buying groceries, and spotting discounts. Here are some key points to help students and shoppers calculate percentages with ease.

Percentage and Fractions Connection

Understanding how fractions, decimals, and percentages are related makes calculating percentages much simpler. Typically, percentages are based on 100, which represents the whole. To convert a fraction to a percentage, you first divide the top number by the bottom number and then multiply by 100. For example, take the fraction 2/5. When you divide 2 by 5, you get 0.4. Multiply that by 100, and you get 40%. So, 2/5 is the same as 40%.

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Percentage of a Whole

To find out what percentage one item is of a group, start by counting the total number of items. Let’s say you have a bowl of candies in different colors. First, count all the candies to get the total number. This total represents 100%. Next, count how many candies you’re interested in and use that number as the top part (numerator) of a fraction, with the total number as the bottom part (denominator). Finally, divide the numerator by the denominator and multiply by 100 to get the percentage.

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Example Problem for Percentage of a Whole

Imagine there’s a bowl of hard candies on the table. There are 15 peppermint, 10 cinnamon, and 35 butterscotch candies. To find out what percentage are peppermint, first add up all the candies: 15 + 10 + 35 = 60. So, there are 60 candies in total, which is 100%. Now, take the number of peppermint candies (15) and divide it by the total number (60). That gives you 0.25. Multiply by 100, and you get 25%. Therefore, 25% of the candies are peppermint.

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Working Backwards from Percentage

Sometimes, you need to find out the original number when you know the percentage. This comes in handy when calculating tips, interest, or sales tax. For example, if you have a meal that costs $35 and you want to leave a 15% tip, you need to figure out what 15% of $35 is.

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Backward Percentage Example

Using the meal example, to calculate a 15% tip on a $35 bill, first convert 15% to a decimal by moving the decimal point two places left, making it 0.15. Then, multiply this by the total bill: $35 × 0.15 = $5.25. So, a 15% tip would be $5.25.

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Calculating Discounts

When shopping, it’s essential to calculate discounts to ensure you’re getting a good deal. Stores often advertise big discounts, but without knowing how to calculate them, you might not realize how much you’re actually saving. For instance, if a shirt costs $55 and is 35% off, knowing how to calculate the final price is crucial.

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Discount Example Method One

Let’s use the $55 shirt with a 35% discount. The first method is to find out how much the discount is in dollars and then subtract it from the original price. To do this, convert 35% to a decimal (0.35) and multiply by $55: 0.35 × $55 = $19.25. This means you save $19.25. Subtract that from the original price: $55 - $19.25 = $35.75. So, the shirt costs $35.75 after the discount.

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Discount Example Method Two

There’s another way to calculate the final price directly. Since the shirt is 35% off, you’re paying 65% of the original price (100% - 35% = 65%). Convert 65% to a decimal (0.65) and multiply by $55: 0.65 × $55 = $35.75. This method also shows that the final price is $35.75, just like the first method.

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Finding the Amount of Interest Paid on a Loan

Understanding how much interest you’ll pay on a loan is crucial, whether it’s for a home or a car. For example, let’s say you take out a $23,000 auto loan with an annual interest rate of 4.21%. To find out how much interest you’ll pay in the first year, convert the percentage to a decimal (0.0421) and multiply it by the loan amount: $23,000 × 0.0421 = $968.30. So, you’d pay $968.30 in interest after the first year.

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The Importance of Percentages

Learning how to work with percentages is a vital skill for anyone dealing with money. Whether you’re shopping for the best deals, budgeting your expenses, or planning for big purchases, knowing how to calculate and understand percentages helps you make smarter financial decisions. Without this knowledge, it’s easy to miss out on savings or end up spending more than you intended.

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