Finding a Percent of a Number

What You’ll Learn

In this lesson you’ll learn two easy ways to find a percent of a number: using decimals or fractions.

The Concept

To find a percent of a number, convert the percent to a decimal (or fraction) and multiply.

Methods:

1. Decimal way: Percent as decimal × number. $20\%$ of $150 = 0.20 \times 150 = 30$

2. Fraction way: Percent as fraction × number. $20\% = \frac{1}{5} → \frac{1}{5} \times 150 = 30$

Same result. Use whichever is easier mentally.

For 10%, 5%, 1%: Move decimal left (10% of 150 = 15), halve for 5%, etc.

Worked Examples

Find 35% of 240 dollars.

1. $35\% = 0.35$
2. $0.35 \times 240 = 84$ dollars

Alternative: $35\% = \frac{35}{100} = \frac{7}{20}$

$\begin{aligned} \frac{7}{20} \times 240 &= \frac{7 \times 240}{20} \\[1em] &= \frac{1680}{20} \\[1em] &= 84 \text{ dollars} \end{aligned}$

Real-World Applications

Finding a percent of a number calculates tips (15% of 60 dollars bill = 9 dollars), discounts (25% of 80 dollars item = 20 dollars off), tax (7% of 300 dollars purchase = 21 dollars tax), or commission (5% of 2000 dollars sales = 100 dollars). It’s a daily skill for money decisions.

You’ve Got This

Convert the percent to a decimal (move two places left) and multiply. That’s the fastest way for most problems. Practice with tips or sales tax you see every day. You’ll get quick and accurate in no time.

Quiz

What is 20% of 150?

• A.30
• B.20
• C.300
• D.15

Find 45% of 80 dollars.

• A.36 dollars
• B.45 dollars
• C.40 dollars
• D.32 dollars

A 15% tip on a 40-dollar meal is how much?

• A.6 dollars
• B.15 dollars
• C.4 dollars
• D.8 dollars

What is 5% of 200?

• A.10
• B.100
• C.5
• D.20

A shirt costs 60 dollars and is 30% off. What is the discount amount?

• A.18 dollars
• B.30 dollars
• C.42 dollars
• D.12 dollars