The 25%-off jacket
A $40 jacket has a '25% off' tag. Twenty-five percent means 25 out of every 100, so you knock off a quarter — $10 — and pay $30. Percentages are just a way of saying 'parts per hundred' that shops, tips, and test scores all use.
Percent means 'per hundred'
A percent expresses a number as a part of 100. So 25% means 25 out of 100, which equals the fraction 25/100 = 1/4 and the decimal 0.25. To find a percent of a number, convert to a decimal and multiply.
Percent of a number
'20% of 80' becomes 0.20 × 80 = 16. Turning the percent into a decimal first makes the arithmetic simple.
A $50 shirt at 30% off: the discount is 0.30 × 50 = $15, so it costs $35.
Lab · Find the percent
- You scored 18 out of 24 on a quiz.
- Write the score as a fraction, then divide.
- Multiply by 100 to get the percent.
What you should see: 18/24 = 0.75, and 0.75 × 100 = 75%.