What a percentage means
A percentage is a part of 100. When you say 25%, you mean 25 out of 100. Percentages are useful because they make different numbers easier to compare.
Basic formula
To calculate a percentage of a number, multiply the number by the percentage and divide by 100.
Example: 20% of 150 = 150 × 20 ÷ 100 = 30.
Percentage increase and decrease
For percentage increase, subtract the old value from the new value, divide by the old value, then multiply by 100. For percentage decrease, subtract the new value from the old value, divide by the old value, then multiply by 100.
When to use it
Use percentages for discounts, taxes, tips, savings, price changes, school math, reports and business comparisons.
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