🔵Understanding Percent as "Out of 100"
What is Percent?
Percent means "per hundred" (cent = 100 in Latin). The symbol % means "out of 100."
- 50% = 50 out of 100 = 50/100 = ½
- 25% = 25 out of 100 = 25/100 = ¼
- 100% = all of it = 1 whole
Real-Life Examples:
- "I got 90% on my test" = answered 90 out of 100 correctly
- "This shirt is 20% off" = save 20 for every100
- "75% of students like pizza" = 75 out of 100 students
PERCENT AS A 100-GRID (10×10):
0% 100%
┌─────────────────────────────────┐
│ │
│ 25% shaded (25 squares) │
│ ░░░░░░░░░░░░░░░░░░░░░░░ │
│ ░░░░░░░░░░░░░░░░░░░░░░░ │
│ │
│ 50% shaded (50 squares) │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
│ │
│ 75% shaded (75 squares) │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
└─────────────────────────────────┘
100% = all 100 squares shaded
PERCENT PIE CHARTS:
25% (¼) 50% (½) 75% (¾)
┌─┐ ┌─┐ ┌─┐
╱ ╲ ╱ ╲ ╱ ╲
│ ░ │ │░░░░░│ │░░░░░│
│ ░░ │ │░░░░░│ │░░░░░│
╲ ╱ ╲ ╱ ╲ ╱
└─┘ └─┘ └─┘👀 See a worked example
What percent is shaded if 45 out of 100 squares are shaded?
- Percent = (part/whole) × 100
- Part = 45, Whole = 100
- 45/100 × 100 = 45%
- Answer: 45%
Write 60% as a fraction in simplest form
- 60% = 60/100
- Simplify: divide both by 20 → (3)/(5)
- Answer: (3)/(5)
What is 30% of 50?
- Method 1: 30% = 30/100 = 0.3, 0.3 × 50 = 15
- Method 2: 30% of 50 = (30/100) × 50 = 1500/100 = 15
- Answer: 15
🤖 Vidi's Key Points
- % means "out of 100"
- To convert % to fraction: put over 100, simplify
- To convert % to decimal: divide by 100
- To find % of a number: multiply by the decimal or fraction
🟢Converting Between Fractions, Decimals, Percents
The Conversion Triangle:
PERCENT
%
↗ ↖
/ \
FRACTION DECIMALConversion Rules:
| From | To | Method |
|---|---|---|
| Percent | Fraction | Put over 100, simplify |
| Percent | Decimal | Divide by 100 |
| Fraction | Decimal | Divide numerator by denominator |
| Decimal | Percent | Multiply by 100 |
| Decimal | Fraction | Write decimal as fraction, simplify |
| Fraction | Percent | Convert to decimal first, then ×100 |
CONVERSION FLOWCHART:
FRACTION ──────divide───→ DECIMAL
↑ │
│ │
simplify multiply
│ │
│ ↓
┌───┴─────────────────── PERCENT
│ put over 100 │
│ divide by 100
│ multiply by 100
↓ │
DECIMAL ←─────write as fraction──┘
COMMON EQUIVALENTS (MEMORIZE!):
Fraction Decimal Percent
───────────────────────────────
½ 0.5 50%
¼ 0.25 25%
¾ 0.75 75%
⅕ 0.2 20%
⅖ 0.4 40%
⅗ 0.6 60%
⅘ 0.8 80%
⅓ 0.333... 33⅓%
⅔ 0.666... 66⅔%
⅛ 0.125 12.5%
⅜ 0.375 37.5%
⅝ 0.625 62.5%
⅞ 0.875 87.5%👀 See a worked example
Convert (3)/(5) to percent
- Method A: (3)/(5) = 0.6, 0.6 × 100 = 60%
- Method B: (3)/(5) = 60/100 = 60%
- Answer: 60%
Convert 0.375 to fraction and percent
- Fraction: 0.375 = 375/1000 = simplify divide 125 → (3)/(8)
- Percent: 0.375 × 100 = 37.5%
- Answer: (3)/(8) and 37.5%
Convert 120% to decimal and fraction
- Decimal: 120% ÷ 100 = 1.2
- Fraction: 120/100 = 12/10 = 6/5 = 1⅕
- Answer: 1.2 and 6/5
🤖 Vidi's Key Points
- Decimal → Percent: multiply by 100 (move decimal 2 places right)
- Percent → Decimal: divide by 100 (move decimal 2 places left)
- Fraction → Decimal: numerator ÷ denominator
- Fraction → Percent: numerator ÷ denominator × 100
- Memorize common conversions (½=50%, ¼=25%, etc.)
🟣Finding Percent of a Quantity
Three Methods to Find Percent of a Number:
Method 1: Convert to Decimal
- 20% of 60 = 0.2 × 60 = 12
Method 2: Use Fraction
- 20% = (1)/(5), so (1)/(5) of 60 = 12
Method 3: Use Proportion
- 20/100 = x/60
- Cross multiply: 100x = 1200, x = 12
Real-World Applications:
- Sales tax: 8% tax on 50 = 0.08 × 50 =4
- Tips: 15% tip on 40 = 0.15 × 40 =6
- Discounts: 25% off 80 = 0.25 × 80 =20 saved
FINDING 20% OF 60 (VISUAL): 0% 20% 100% ├──────────────────────┼──────────────────────┤ │ │ │ 0 12 60 20% of 60 = 12 PERCENT OF A NUMBER - BAR MODEL: 60 total (100%) ┌────┬────┬────┬────┬────┐ │ 12 │ 12 │ 12 │ 12 │ 12 │ └────┴────┴────┴────┴────┘ 20% 20% 20% 20% 20% Each 20% = 12 DISCOUNT CALCULATION: Original Price: 80 (100%) 25% Discount = 20 saved ┌─────────────┬─────────────┐ │ 20 saved │ 60 pay │ │ (25%) │ (75%) │ └─────────────┴─────────────┘ Final Price: 60
👀 See a worked example
Find 15% of 200
- Decimal: 0.15 × 200 = 30
- Fraction: 15/100 × 200 = 3000/100 = 30
- Answer: 30
A shirt costs 40. It is 30% off. How much do you save?
- 30% of 40 = 0.3 × 40 = 12
- Answer: 12 saved
There are 25 students. 40% are girls. How many are girls?
- 40% = 0.4
- 0.4 × 25 = 10
- Answer: 10 girls
🤖 Vidi's Key Points
- "Percent of" means multiply
- Convert percent to decimal or fraction first
- Of = multiplication (×)
- Is = equals (=)
- Check if answer makes sense (part < whole for % < 100%)
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