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Learn: Percentages in Mathematics
iGCSE Mathematics
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Welcome!Today we'll learn all about percentages. Percentages are a way to express numbers as parts of 100, and they are very useful in everyday life!
What are Percentages?A percentage is a fraction out of 100. The symbol for percentage is %. For example, 25% means 25 out of 100, or 1/4.
Why are Percentages Important?Percentages help us compare quantities easily, calculate discounts, and understand proportions. For example, you might use percentages to calculate a sale price or find how much interest you earn on savings.
Quick check: What does 50% mean?
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Calculating Percentage of a NumberTo find the percentage of a number, multiply the number by the percentage (as a decimal or fraction) and divide by 100. For example, 20% of 50 = (20/100) × 50 = 10.
To calculate the percentage, multiply the number by the {{blank0}} (as a decimal or fraction) and divide by {{blank1}}.
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Example: Finding the PercentageLet's try an example. What is 30% of £200? Step 1: Turn 30% into a fraction (30/100). Step 2: Multiply by £200. So, (30/100) × 200 = £60. 30% of £200 is £60.
Match the items on the left with their correct pairs on the right
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Percentage Increase and DecreaseA percentage increase means adding a percentage of a number to itself. A percentage decrease means subtracting a percentage of a number from itself.
Calculating Percentage ChangeTo calculate the percentage change, use the formula:Percentage change = \frac{difference}{original\ value} \times 100This helps you find how much a value increases or decreases compared to the original.
If a £40 item is increased by 10%, what is the new price?
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Reverse PercentagesTo find a number before a percentage change, divide the new value by (1 + percentage change for increase or 1 - percentage change for decrease).
To calculate the original price before a percentage increase, divide the new price by {{blank0}}.
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Review Time!Great work! You've learned about percentages, including calculating a percentage, percentage change, and reverse percentages. Let's review with some practice questions.
Which of the following statements are true about percentages? (Select all that apply)
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Match the items on the left with their correct pairs on the right
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Match the items on the left with their correct pairs on the right
Start the lesson to answer this matching question
Match the items on the left with their correct pairs on the right
Start the lesson to answer this math equation question
Well done!You’ve completed the lesson on percentages. Keep practising to strengthen your skills further and you'll master this topic in no time!
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