Learn How to Work Out a Fraction of an Amount - KS3 Maths (BBC Bitesize)

Key Points

• Finding a Fraction of an Amount:
  • Divide by the denominator (bottom number of the fraction).
  • Multiply by the numerator (top number of the fraction).
  • This process can be performed in any order.
  • A bar model can help visualize the problem.
• Reversing the Process:
  • When given a fractional amount and needing to find the whole,
    • Divide by the numerator.
    • Multiply by the denominator.

How to Find a Fraction of an Amount

1. Divide the total amount by the fraction’s denominator.
2. Multiply the result by the numerator.

Using a Bar Model

1. Draw a bar to represent the total amount.
2. Split the bar into parts as defined by the denominator.
3. Find the value of one part by dividing the amount by the number of parts.
4. Multiply the result by the numerator to find the required fraction.

Examples

• Example 1:
  • 3/4 of 80: Divide 80 by 4, then multiply by 3. Result: 60
• Example 2:
  • 2/3 of 24: Divide 24 by 3, then multiply by 2. Result: 16
• Example 3:
  • 2/5 of 18: Divide 18 by 5, then multiply by 2. Result: 7.2

Question

• Example Question: Calculate 3/10 of 560.
  • Divide 560 by 10, then multiply by 3. Result: 168

How to Find the Amount from a Given Fraction

1. Divide by the numerator to find the unit fraction.
2. Multiply by the denominator to find the whole amount.

Examples

• Example 1:
  • 3/4 of a number is 24. To find the number: (24/3)*4 = 32
• Example 2:
  • 5/9 of a number is 20. To find the number: (20/5)*9 = 36

Question

• If 3/5 of a number is 36, what is the number?
  • Divide 36 by 3, then multiply by 5. Result: 60

Practise

• Engage in quizzes to practice finding fractions of amounts.

Real-World Applications

• Architects frequently use fractions in design plans.
  • For example, floor plans might be 1/50th the size of the actual building.

Interactive Learning

• Game: Play the "Divided Islands" game to practice math skills through engaging activities.
• Further Topics:
  • Converting between fractions, decimals, and percentages.

These notes provide a structure to understand and practice the calculation of fractions of amounts, implementing real-world applications and interactive tools for enhanced learning.