B1 Summary chapter Percentages



What Have I Learned?

Fractions and Percentages

Fractions

[pic]

• Equivalent fractions

× 5

[pic] = [pic]

× 5

•

• Simplifying fractions

We can divide both the numerator and the denominator by the SAME number to simplify a fraction.

÷ 7

[pic] = [pic]

÷ 7

• Fractions of a quantity:

Examples

Percentages

• Percentage means out of 100.

• A percentage may be written as an equivalent fraction and decimal

|Percentages |Fraction |Decimal |

|1% |[pic] |0∙ 01 |

|10% |[pic] |0 ∙1 |

|20% |[pic] |0 ∙2 |

|25% |[pic] |0 ∙25 |

|50% |[pic] |0 ∙5 |

|75% |[pic] |0 ∙75 |

|33 ⅓ % |[pic] |0∙ 33 |

|66 ⅔ % |[pic] |0∙ 67 |

|12.5% |[pic] |0.125 |

Some percentages are in common usage.

• Common Percentages

• Be able to calculate percentages without a calculator using:-

1% =[pic] or 10% = [pic]

• Be able to calculate percentages with a calculator.

56% of 130ml

0.56 x 130 = 72.8ml

• To change a fraction to a percentage; eg: - [pic] = 45 ÷60 = 0.75=75%

• Percentage Increase and decrease

When the value of an item increases we ADD the percentage on to the original value.

When an item decreases in price we SUBTRACT the percentage from the original value.

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To calculate 7% of £160

1% of £160

= [pic] of £160

= £1.60

Then 7% of £160 = 7 × £1.60 = £11.20

To calculate 40% of £48

10% of £48

= [pic] of £48

= £4.80

Then 40% of £48 = 4 × £4.80 = £19.20

Remember: Divide by the bottom, multiply by the top

denominator

numerator

Calculate

[pic] of 33g

= 33g ÷ 3

= 11g

So 11g × 2

= 22g

Calculate

[pic] of £200

= £250 ÷ 5

= £50

So £50 × 1

= £50

We can multiply both the numerator and the denominator by the SAME number to calculate an equivalent fraction.

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