Percentages Solutions

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2. Simply write them as a fraction of 72 and then multiply by 100.
a) 25% b) 33.3% c) 20% d) 75% e) 12.5% f) 62.5%

3. 17.5% of �16 Can be calculated as follows:
  • 10% of �16 is �1.60
  • Halving to give 5% is �0.80
  • Halving again to give 2.5% is �0.40
  • 17.5% of �16 is then �1.60 + �0.80 + �0.40 = �2.80
So the bill comes to �16 + �2.80 = �18.80 Another way to have done this is to calculate 117.5% of �16.
4. Either calculate 80% of �75 by using equivalent decimals so that

  • 0.8 × 75 = �60 or

  • Find 10% of �75 = �7.50
  • Doubling this to get 20% which is �15
  • Subtract this from �75 so that we have �60.

    5.

    36 ÷ 0.8 = �45 or use the unitary method.

    • 80% is 36
    • so 1% is 36 ÷ 80
    • = 0.45
    • so 100% is 0.45 × 100 = �45
    		6.
    • 26-20 = 6
    • 6 ÷ 20 = 0.3
    • As a percentage this is 0.3 × 100 = 30%
    7.
    • John's rate of interest: (6/150) × 100 = 4%
    • Jane's rate of interest: (5.4/120) × 100 = 4.5%
      So Jane's rate is better.
    8.
    1. 5% of �3000 is �150 so in 4 years he will have �3000 + 4×(�150) = �3600
    2. 3000 × ( 1.05)4. Don't worry if you didn't get this, it will be covered in a later chapter.

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