📖Definition
A percentage is a way of expressing a number as a fraction of 100. The word "percent" means "per hundred," so 45% means 45 out of 100, or 45/100, or 0.45 as a decimal.
📐Formula
To find what percentage one number is of another, divide the part by the whole, then multiply by 100. For example, 15 out of 60 = (15/60) × 100 = 25%.
📝Step-by-Step Guide
Finding a Percentage of a Number
Convert the percentage to a decimal (divide by 100), then multiply by the number.
Finding What Percentage One Number Is of Another
Divide the part by the whole, then multiply by 100.
Percentage Increase
Calculate the increase, divide by the original value, multiply by 100.
Percentage Decrease
Calculate the decrease, divide by the original value, multiply by 100.
⚠️Common Mistakes to Avoid
- Dividing by the new value instead of the original when calculating percent change
- Forgetting to multiply by 100
- Confusing percentage increase with the final amount
- Moving the decimal point the wrong way when converting
✏️Practice Problems
What is 25% of 80?
Answer: 20
A shirt was $40 and is now $32. What is the percentage decrease?
Answer: 20%
After a 15% increase, a price is $92. What was the original price?
Answer: $80
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