The Multiplier Method
Mastering Repeated Changes & Compound Interest
Mode A: The Multiplier Machine
Multiplier: ×1.50
Multiplier: ×0.50
£100
Start
×1.50
£150.00
After 1st
×0.50
£75.00
Final
Net Change
-25.00%
⚠️ TRAP: +50% then -50% ≠ 0%! The second % acts on a DIFFERENT amount!
Combined Multiplier:
×0.7500
1.50 × 0.50
Mode B: Interest Simulator
Simple Interest
Compound Interest
Simple (Year 5)
£1250.00
Linear Growth
Compound (Year 5)
£1276.28
Exponential Growth
Compound Power
It's not magic, it's powers! Multiply by 1.05 5 times:
1000 × (1.05)^5
Dynamic Solver: Compound Calculator
Cambridge-Style Working:
Formula: A = P(1 + r/100)^n
Step 1: Find multiplier
1 + 3/100 = 1.0300
Step 2: Raise to power
(1.0300)^4 = 1.125509
Step 3: Multiply by principal
5000 × 1.125509
Step 4: Calculate
= £5627.544050
Final Amount (A)
£5627.54
Total Interest:+£627.54
Percentage Change:+12.55%
Formula Used:5000 × (1.03)^4
Edexcel Mark Scheme Rules
- Always show the multiplier calculation: 1 ± (r/100)
- Write the formula BEFORE substituting numbers
- Show at least 4 significant figures in intermediate steps
- Round final answer to 2 decimal places for money
- For depreciation, remember it's (1 - r/100), not (1 + r/100)
- State your final answer clearly: "Final amount = £..."
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