Maths Library

Percentage Increase and Decrease: Year 8 maths

This topic covers increasing and decreasing quantities by a given percentage, as well as calculating percentage change. Students practise using additive steps and single-step multiplier methods.

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What this covers

Percentage Increase and Decrease is taught in Year 8 (age 13 to 14) as a main teaching focus. It sits in the Percentages strand.

Worked example

Increase 80 by 15%

  1. Find 10%: 8010 = 8
  2. Find 5%: 82 = 4
  3. Total increase: 8 + 4 = 12
  4. Add to original: 80 + 12 = 92

Answer: 92

Difficulty scale

The sheet generator offers five difficulty settings for this topic.

  1. Integer increases/decreases using 10%, 20%, or 50% on simple numbers
  2. Increases/decreases using multiples of 5% on 2-digit or 3-digit values
  3. Any integer percentage increase/decrease using multiplier methods
  4. Calculating percentage change given original and new values
  5. Reverse percentage problems or multi-step word problems involving compound change

Common mistakes

  • Subtracting or adding the percentage value directly (e.g. 50 + 10% = 60.1)
  • In reverse problems, calculating percentage of the final amount instead of the original

Curriculum links

Indicative matches to Australian Curriculum v9. Check wording and codes against the official document.

  • AC9M8N04 Solve practical problems involving ratios, rates, and percentage change.

Sample sheet and answers

Six questions at the level's usual difficulty. Open the editor to change, add or regenerate any of them.

Percentage Increase and Decrease

Year 8 maths

Qs
6
Marks
12
NameDateScore / 12
1.
A coat costs $160.00. In a sale the price rises by 10%. Find the new price.
[2]
2.
A coat costs $260.00. In a sale the price falls by 30%. Find the new price.
[2]
3.
A coat costs $360.00. In a sale the price rises by 20%. Find the new price.
[2]
4.
A coat costs $400.00. In a sale the price falls by 10%. Find the new price.
[2]
5.
A coat costs $60.00. In a sale the price rises by 10%. Find the new price.
[2]
6.
A coat costs $100.00. In a sale the price rises by 30%. Find the new price.
[2]

Answer key

  1. $176.00The multiplier is 1.1; $160.00 × 1.1 = $176.00
  2. $182.00The multiplier is 0.7; $260.00 × 0.7 = $182.00
  3. $432.00The multiplier is 1.2; $360.00 × 1.2 = $432.00
  4. $360.00The multiplier is 0.9; $400.00 × 0.9 = $360.00
  5. $66.00The multiplier is 1.1; $60.00 × 1.1 = $66.00
  6. $130.00The multiplier is 1.3; $100.00 × 1.3 = $130.00