High School Maths Examples and Questions

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Answers − Percentage Change

1.   The original price is 500 and the new price is 700.

  Find the percentage increase

  (a)   the increase amount is 700 − 500 = 200
  (b)   the percentage as a fraction is 200/500 = 2/5
  (c)   100 ÷ 5 = 20 (where 5 is the demoninator of the fraction)
  (d)   2/5 × 20/20 = 40/100 = 40%
  So 40% increase in price

2.   The original price is 470 and the new price is 564.

  Find the percentage increase

  (a)   the increase amount is 564 − 470 = 94
  (b)   the percentage as a fraction is 94/470 = 1/5
  (c)   100 ÷ 5 = 20 (where 5 is the demoninator of the fraction)
  (d)   1/5 × 20/20 = 20/100 = 20%
  So 20% increase in price

3.   The original price is 50 and the new price is 40.

  Find the percentage decrease

  (a)   the decrease amount is 50 − 40 = 10
  (b)   the percentage as a fraction is 10/50 = 1/5
  (c)   100 ÷ 5 = 20 (where 5 is the demoninator of the fraction)
  (d)   1/5 × 20/20 = 20/100 = 20%
  So 20% decrease in value.

4.   The original price is 1100 and the new price is 990.

  Find the percentage decrease

  (a)   the decrease amount is 1100 − 990 = 110
  (b)   the percentage as a fraction is 110/1100 = 1/10
  (c)   100 ÷ 10 = 10 (where 10 is the demoninator of the fraction)
  (d)   1/10 × 10/10 = 10/100 = 10%
  So 10% decrease in value.

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