🧱 See It
The percent → decimal → multiply method from before doesn't change. What changes is the everyday situation it's used in, and whether the result gets added to a price or subtracted from it.
✏️ Draw It
| Situation | What happens to the price |
|---|---|
| Sales Tax | find the amount, then ADD it |
| Tip | find the amount, then ADD it |
| Discount | find the amount, then SUBTRACT it |
The percent → decimal → multiply step never changes — only what happens after it does.
🔢 Write It
amount = percent (as a decimal) × original price
final = original price ± amount
Plus for tax and tips. Minus for discounts. Decide which one BEFORE calculating anything.
💡 Worked Examples
Example 1 — Sales Tax: a $40 item with 8% sales tax
- Turn the percent into a decimal:
8% = 0.08 - Find the tax amount:
0.08 × 40 = $3.20 - Add to the original price:
$40 + $3.20 = $43.20 - Answer: $43.20
Example 2 — Tip: a $25 restaurant bill with an 18% tip
- Turn the percent into a decimal:
18% = 0.18 - Find the tip amount:
0.18 × 25 = $4.50 - Add to the original bill:
$25 + $4.50 = $29.50 - Answer: $29.50
🧠 Quick Reference
Same method every time: percent → decimal → multiply by the original price. Tax and tips ADD to the price. Discounts SUBTRACT from the price. Always write the amount and the final total as two separate labeled lines.