Learn how to find the percentage of any number in 2 steps. Method: multiply by decimal equivalent. 15% of 200 = 0.15 × 200 = 30. With 15 examples and mental math tricks.
Method: convert % to decimal (divide by 100), then multiply. 15% of 200 → 0.15 × 200 = 30. Quick tricks: 10% = move decimal left. 50% = divide by 2. 25% = divide by 4.
| % | Shortcut | Example (of 80) |
|---|---|---|
| 10% | Move decimal left 1 | 8 |
| 20% | 10% × 2 | 16 |
| 25% | Divide by 4 | 20 |
| 50% | Divide by 2 | 40 |
| 75% | 50% + 25% | 60 |
| 1% | Move decimal left 2 | 0.8 |
Siempre sustituye tu respuesta en el problema original para confirmar que es correcta.
Los errores ocurren cuando se trata de hacer todo mentalmente. Escribe cada paso.
Lee el problema dos veces antes de resolver. Identifica qué te dan y qué te piden.
Esta técnica aplica en exámenes de secundaria, preparatoria y universidad. Es fundamental dominarla antes de pasar a temas más avanzados.
Bill is $65. Standard 15% tip: $65×0.15=$9.75. Quick way: 10%=$6.50, 5%=$3.25, total=$9.75.
Item costs $299. Tax is 8%: $299×0.08=$23.92. Total: $299+$23.92=$322.92.
Got 42 out of 60 points. (42÷60)×100=70%. You passed!
$150 jacket, 30% off. Savings: $150×0.30=$45. You pay: $150−$45=$105.
"15% of $200" = $30 (the amount). "15% off $200" = $200−$30=$170 (the final price). Very different results!
Whole = Part ÷ (Percentage/100). 30 is 15% of what number? 30÷0.15=200.
Percent means "per hundred." 15% = 15/100 = 0.15. Multiplying by 0.15 is the same as finding 15 out of every 100.
Percentage = (Part / Whole) × 100. Example: 15 out of 60 = (15/60)×100 = 25%
Part = Whole × (Percentage/100). 30% of 80 = 80×0.30 = 24
Whole = Part ÷ (Percentage/100). 24 is 30% of what? 24÷0.30 = 80
There are three types of percentage problems: (1) find the percentage given part and whole, (2) find the part given whole and percentage, (3) find the whole given part and percentage. Identify which type you have before solving.
Percentage problems appear constantly in real life: tip calculations, tax rates, test scores, discounts, and statistics. The three types (find %, find part, find whole) cover every scenario. Identify which quantity is unknown before choosing your approach.