Percent of a Number
Find p percent of a number N.
Formula
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Example
20% of 150 = 30
How it works
A percent is just a fraction out of 100, so p% means p/100. To find that part of a number, you multiply the whole amount N by p/100, which scales the number down to the correct portion. For example, 25% means one quarter, and 50% means one half, so the formula turns percentage language into ordinary multiplication.
When to use it
Use this when you need to find a part of a total, such as a discount, tax, tip, test score, or growth amount. It is useful any time a problem says "what is p% of N?"
Worked example, step by step
Find 15% of 80 value = (p/100) × N value = (15/100) × 80 value = 0.15 × 80 value = 12 So, 15% of 80 is 12.
Common mistakes to avoid
- Multiplying by p instead of p/100
- Using the wrong whole number N
- Forgetting that percent means "out of 100"
Did You Know?
Merchants in ancient Rome levied a tax called centesima rerum venalium — a 1% duty on goods sold at auction, an early real-world percentage.
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