Question 1

How do I calculate a percentage of a number?

Accepted Answer

To find X% of a number Y, divide X by 100 and multiply by Y. For example, to find 25% of 80: (25/100) x 80 = 20. This works because 'percent' literally means 'per hundred.'

Question 2

How do I find what percentage one number is of another?

Accepted Answer

Divide the part by the whole and multiply by 100. For example, if you scored 45 out of 60 on a test: (45/60) x 100 = 75%. This tells you that 45 is 75% of 60.

Question 3

What is the difference between percentage change and percentage difference?

Accepted Answer

Percentage change measures the change from an original value to a new value: ((new - old) / |old|) x 100. Percentage difference compares two values without a clear 'original': (|A - B| / ((A + B) / 2)) x 100. Use percentage change when there is a clear before/after relationship.

Question 4

Can a percentage be greater than 100%?

Accepted Answer

Yes. A percentage greater than 100% simply means that the value exceeds the reference amount. For example, if a stock price goes from $50 to $150, the percentage change is 200%, meaning it tripled in value.

Question 5

How do I reverse a percentage? For example, if a price after 20% discount is $80, what was the original?

Accepted Answer

If a 20% discount results in $80, the discounted price represents 80% of the original (100% - 20% = 80%). So the original price = $80 / 0.80 = $100. In general, original = discounted price / (1 - discount rate).

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