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Class 5 Maths Adventure

Percentages

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🔵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   DECIMAL

Conversion Rules:

FromToMethod
PercentFractionPut over 100, simplify
PercentDecimalDivide by 100
FractionDecimalDivide numerator by denominator
DecimalPercentMultiply by 100
DecimalFractionWrite decimal as fraction, simplify
FractionPercentConvert 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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