3.4.2

Direct Proportion

Test yourself

Direct Proportion

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Notation

  • This means y is proportional to x.
  • This means there is some number k such that y = kx.
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Proportional to x²

  • If y is proportional to x2 then we write y α x2 and there is some number k such that y = kx2.
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Example

  • Four bananas cost 80p. How much will 7 bananas cost?
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Example

  • Four bananas cost 80p. How much will 7 bananas cost?
    • Find the cost of one banana. This is the value of k.
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Example

  • Four bananas cost 80p. How much will 7 bananas cost?
    • Seven bananas will cost 7 × 20p = £1.40.

Jump to other topics

1Number

1.1Place Value

1.2Factors & Multiples

1.3Operations

1.4Fractions, Decimals & Percentages

1.5Growth & Decay

1.6Measurements & Units

1.7Accuracy

2Algebra

3Ratio, Proportion & Rates of Change

4Geometry & Measures

5Probability

6Statistics

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