IGCSE Maths / Ratios and percentages
Depreciation and decay
Edexcel International GCSE Maths (4MA1), chapter 2: Ratios and percentages, specification point 1.6a. Part of the full course.
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Depreciation is a repeated percentage decrease in value. Use a multiplier below 1 for each year, raised to the number of years, because each year's percentage is taken off the current value.