Shopping & Consumer CostsSequential Math
Double Discount Calculator
Calculate sequential discounts correctly (e.g., 30% store sale plus an extra 20% coupon). Understand why sequential discounts do not simply add up.
Final Price:$0.00
After 1st Discount:$0.00
Effective Combined Discount:0.0%
Sequential discounting note...
Sequential Double Discount Formula
Price After 1st = Original × (1 - D1); Final Price = Price After 1st × (1 - D2); Effective Discount % = (1 - (1 - D1)(1 - D2)) × 100- Sequential Compounding: The second discount applies only to the already reduced balance, never to the full original retail price.
- Arithmetic Fallacy: A 20% store sale plus a 20% VIP coupon yields a 36% total discount ($100 → $80 → $64), NOT a 40% discount.
Step-by-Step Worked Example
Scenario:
Calculation Steps:
Result:
How to Use This Calculator
Assumptions & Limitations
- Assumes store terms permit coupon stacking on top of clearance or promotional items.
Frequently Asked Questions
Why doesn't 30% off plus 20% off equal 50% off?
Because the second 20% discount is applied to the discounted $70 price ($14 savings), not the original $100 price ($20 savings). You save $30 + $14 = $44 total (44% off), which is 6% less than adding the numbers together.
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