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Percentages Help

Find a percent of a number, percent increase and decrease, discounts, and what percent one number is of another.

Percent means “out of 100”. To use a percent in a calculation, turn it into a decimal by dividing by 100 (for example 15% = 0.15), then multiply.

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Example problems & solutions

Q

What is 15% of 80?

A
  1. Change 15% to a decimal: 15 ÷ 100 = 0.15.
  2. Multiply: 0.15 × 80 = 12.

Answer: 12

Q

What percent of 50 is 18?

A
  1. Divide the part by the whole: 18 ÷ 50 = 0.36.
  2. Multiply by 100 to get a percent: 0.36 × 100 = 36%.

Answer: 36%

Q

A price goes from $40 to $50. What is the percent increase?

A
  1. Find the change: 50 − 40 = 10.
  2. Divide by the original amount: 10 ÷ 40 = 0.25.
  3. Convert to a percent: 0.25 × 100 = 25%.

Answer: 25% increase

Q

A $60 jacket is 30% off. What is the sale price?

A
  1. Find the discount: 30% of 60 = 0.30 × 60 = 18.
  2. Subtract it from the original price: 60 − 18 = 42.
  3. Shortcut: paying 70% of the price gives 0.70 × 60 = 42 too.

Answer: $42

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Frequently asked questions

How do you find a percentage of a number?

Divide the percent by 100 to make a decimal, then multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.

How do you calculate percent change?

Subtract the old value from the new value, divide by the old value, and multiply by 100. A positive result is an increase and a negative one is a decrease.

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