Variable Key
What is X% of Y?
Find the part given the percentage and the whole.
X is what % of Y?
Find the percentage given part and whole.
Percentage change
Measure relative increase or decrease.
Percentage of percentage
Compute a percentage of another percentage.
Increase / Decrease by %
Apply a percentage to change a value.
A percentage represents a ratio expressed as a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." Percentages are used everywhere: discounts, test scores, tax rates, nutrition labels, and statistics.
Pro Tip
Mental math shortcut: 10% of any number = move the decimal left once. Then multiply for other percentages. 35% = 30% + 5% = (3 × 10%) + (10%/2).
Did You Know?
The percent sign (%) evolved from the Italian "per cento." By the 17th century, it was being written as "p100" or "p/100", which gradually became the % symbol we use today.
References