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Digital Growth Engine

Mathematics · Topic

Percentage change, including repeated change over time

Use a multiplier (for example 1.06) rather than calculating year by year, and keep money to two decimal places.

2 original questions in the bank, worth 5 marks · above the two-per-topic floor

Drill this topic All percentage change, including repeated change over time questions

The questions, with the examiner reasoning

Work out3 marksBGCSE

A bakery spends P4,800 a year on fuel. The cost rises by 6% in the first year, and the new amount rises by a further 4% in the second year. Work out the fuel cost after two years.

Show the mark scheme and the examiner note

Answer: P5,291.52

  1. Year one: 4800 × 1.06 = 5088
  2. Year two: 5088 × 1.04 = 5291.52
  3. Money to two decimal places: P5,291.52

Examiner technique: Two separate percentage rises never add up to 10%. Use a multiplier for each year and keep every digit until the final rounding.

Show that2 marksIGCSE

A jacket is marked at P1,250. In a sale the price falls by 20%. The sale price is later increased by 20% to become the new normal price. Show that the new normal price is P1,200.

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Answer: P1,250 × 0.80 = P1,000; P1,000 × 1.20 = P1,200

  1. Sale price: 1250 × 0.80 = 1000
  2. New price: 1000 × 1.20 = 1200

Examiner technique: This is the 20%-up-is-not-20%-down trap. Both marks belong to the two calculations; the answer is already printed, so quoting it earns nothing.