Solve any common percentage question here — what is X% of Y, what percent X is of Y, and the percentage increase or decrease between two numbers.
A percentage is just a part out of 100, so 25% is the same as 0.25.
For percentage change, always divide the difference by the original (old) number, not the new one.
A positive answer means an increase. A negative answer means a decrease.
X% of Y: Y × X ÷ 100
X as a % of Y: X ÷ Y × 100
% change: (New − Old) ÷ Old × 100
Why isn't a 50% increase cancelled out by a 50% decrease?
Because each percentage is worked out on a different starting number. 100 increased by 50% becomes 150. But 150 decreased by 50% becomes 75, not 100 — because the decrease is worked out on the bigger number, 150.
What is the difference between percentage points and percent?
If a rate goes from 5% to 7%, that is a rise of 2 percentage points, but it is also a 40% increase. Mixing up these two is a common mistake in news reports.