This deep dive covers The 5-Step Growth & Decay Method within Growth & Decay for GCSE Mathematics. Revise Growth & Decay in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 8 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 8
Practice
12 questions
Recall
22 flashcards
The 5-Step Growth & Decay Method
Step 1: Identify the Type
Is the quantity increasing (growth) or decreasing (decay)?
- Growth: Population, investment, bacteria, viral spread
- Decay: Radioactivity, drug concentration, car value, cooling
Step 2: Convert Percentage to Decimal
Change the percentage rate to decimal form:
- 5% = 0.05
- 12% = 0.12
- 0.5% = 0.005
Step 3: Find the Multiplier
- Growth: (1 + r) where r is the decimal rate
- Decay: (1 - r) where r is the decimal rate
Examples: 5% growth → 1.05, 12% decay → 0.88
Step 4: Apply the Formula
- Growth: N = N₀ × (1 + r)ⁿ
- Decay: N = N₀ × (1 - r)ⁿ
Where n is the number of time periods
Step 5: Calculate and Check
Substitute values and calculate. Always check:
- Does the answer make sense?
- Is growth increasing and decay decreasing?
- Are units correct?