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Percentages

🟦📊 Technique Card: Understanding Percentages (deeper)

Big Idea: A percentage is a part out of 100. It helps us fairly compare data — especially when group sizes are different.
Useful for: Surveys, school projects, spreadsheets, and digital changemaker work.

🧠 What Is a Percentage?

A percentage tells you how many out of 100.

  • 32% means 32 children out of every 100
  • 100% means everyone
  • 50% means a half
  • 25% means one quarter
  • 0% means nobody

It helps us understand how big a part is — even when totals are different.

🚌 Survey Example: How Children Get to School

At a school of 210 students, a survey showed:

Travel Type Number of Students
Walk 84
Bike 21
Car 63
Bus 42
Total 210

Let’s work out the percentage who walk to school.

👉 Step-by-Step:

  1. Divide the part by the total:
    84 ÷ 210 = 0.4

  2. Multiply by 100:
    0.4 × 100 = 40%

✅ So 40% of children walk to school.

🔍 Why Percentages Matter

Percentages help you:

  • Compare different groups fairly
  • Understand how big or small a part is
  • Spot important patterns or problems
  • Show change (like how much CO₂ has gone up or down)

💡 Why Use Percentages?

Percentages let us compare schools fairly.

Say another school has 525 students, and 210 of them walk.

  • That’s 210 ÷ 525 = 0.4
  • 0.4 × 100 = 40%

Even though one school has more children walking, both have 40% — so the walking rate is the same.

📊 Percentages give a fair picture.

🧮 Quick Formula

Percentage = (Part ÷ Total) × 100

Use this when:

  • Comparing data from different schools or places
  • Showing results from a class or school survey
  • Making graphs or explaining trends

Do you:

  • Want to know what percentage of fish are endangered?
  • Or what percentage of your food is local?
  • Or how much a number has increased or decreased?

Use the formula every time!

🧠 Extra: What Does 32% Really Mean?

If 32% of children come by car:

  • In a school of 100 → 32 children
  • In a school of 210 → 32 ÷ 100 × 210 = 67.2 → about 67 children
  • In a school of 525 → 32 ÷ 100 × 525 = 168 → 168 children

You can also reverse it to find percentages from numbers.

🧠 Even Extra! Increase and Decrease by Percent

Want to know how much something has changed?

Say fish population went from 2000 to 1600.

  1. Find the change:
    2000 - 1600 = 400

  2. Divide the change by the original:
    400 ÷ 2000 = 0.2

  3. Multiply by 100:
    0.2 × 100 = 20% decrease

📉 The fish population went down by 20% ☹️

🎯 When You Might Use This

  • Creating infographics for digital changemaker campaigns
  • Surveys about travel, food, energy use
  • Comparing school data across sizes
  • Scratch games with chance (e.g. 25% chance to win!)
  • Making spreadsheets more useful and visual
  • Digital changemakers exploring data to help the world
  • Graphs and infographics to explain your ideas
  • Budgets and surveys — how many people agree?

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