Shopping Spree Slides 7TH GRADE MATH
Percent Power
Shopping
Mastering Tax, Tips, and Discounts
Why isn't it just $20?
You see a pair of shoes for $50.00. When you get to the register, you pay $54.38.
You order a burger for $12.00. The menu says "20% OFF Today!" How much do you actually pay?
The Real World Math
TAX & TIPS = ADDED
DISCOUNTS = SUBTRACTED
The 3-Step Percent Strategy
1
Convert
Turn your Percent into a Decimal.
Divide by 100 or move the decimal 2 places left.
8% → 0.08
2
Multiply
Multiply the Original Price by that Decimal.
$50 × 0.08 = $4.00
3
Adjust
Add (Tax/Tip) or Subtract (Discount) from the original.
$50 + $4 = $54
SALE! 25% OFF
Example: New Headphones
The Scenario:
Headphones cost $80.00.
1
25% → 0.25
2
$80 × 0.25 = $20.00 (The Discount)
3
$80 - $20 = $60.00 (Final Price)
TECH DEPOT
Order #7890
HEADPHONES $80.00
25% DISCOUNT -$20.00
TOTAL $60.00
Dinner & Drinks
The Bill Details
Pizza Subtotal: $24.00
Sales Tax: 8%
Server Tip: 20%
Pro Tip: Calculate tax and tip separately on the Original Subtotal.
Calculations
Tax: $24 × 0.08 = $1.92
Tip: $24 × 0.20 = $4.80
Final Checkout
$24.00 + $1.92 + $4.80 = $30.72
Quick Checkout Challenge
SOLVE BEFORE THE TIMER ENDS!
Scenario A
A Coffee Shop bill is $15.00.
TOTAL: $_________
Scenario B
A Jacket costs $120.00.
SALE PRICE: $_________
Marketplace Math Worksheet Marketplace Math
Mastering the Art of the Deal
NAME:
DATE:
The Rulebook: 1. Convert percent to decimal (÷ 100). 2. Multiply by original price. 3. ADD for tax/tips. SUBTRACT for discounts.
Part 1: The Daily Diner
Ticket #01
You and a friend share a pizza and wings. The total bill comes to $32.50. You want to leave a 18% tip for the great service.
TIP AMOUNT:
TOTAL BILL:
Ticket #02
A family breakfast costs $45.00. The city has a 8.5% sales tax. Calculate the tax and the final cost after tax.
TAX AMOUNT:
TOTAL BILL:
Part 2: The Designer Boutique
Clearance Event!
Everything must go. Calculate the savings and the final "New Price".
Item
Winter Parka
Orig: $180
35% OFF
SALE PRICE:
Item
Running Shoes
Orig: $95
15% OFF
SALE PRICE:
Item
Sunglasses
Orig: $42
60% OFF
SALE PRICE:
Part 3: The Multi-Step Challenge
Scenario: The Gaming Console Deal
A gaming console costs $400.00.
Step 1: Calculate Sale Price
Step 2: Calculate Tax on Sale Price
Final Price:
Quick Checkout Exit Ticket Quick Checkout
EXIT TICKET
STUDENT NAME
SCORE
/ 10
1
The Sneaker Sale
A pair of sneakers costs $85.00. They are on sale for 30% OFF. What is the final sale price?
Show your work
SALE PRICE:
2
The Cafe Bill
Your lunch bill is $22.00. You want to leave a 20% tip. What is the total amount you will pay?
Show your work
TOTAL:
Spot the Mistake
"To find the cost of a $50 shirt with a 10% tax, I multiply 50 × 0.10 to get $5.00. Then I subtract $5.00 from $50 to get a total of $45."
What is wrong with this student's thinking?
Shopkeeper Secrets Teacher Guide Teacher Resources
Shopkeeper Secrets
Instructional Guide: Percent Applications
Target Standard
CCSS.MATH.7.RP.A.3
Lesson Flow
01
The Hook (5-7 mins)
Use Slide 2 to discuss the "Surprise Total" at registers. Ask students if they've ever been surprised by the tax or a tip at a restaurant.
02
Direct Instruction (15 mins)
Model the 3-Step Strategy (Slide 3). Emphasize that "Convert" and "Multiply" are always the first steps. The "Adjust" step is where the type of application matters.
03
Guided Practice (15 mins)
Use Slides 4-6. Walk through the headphone discount and the dinner bill. Let students attempt Scenario A/B before revealing answers.
04
Independent Work (20 mins)
Students complete the "Marketplace Math" worksheet. Circulate to check for multi-step errors (e.g., applying tax to original price instead of sale price).
Key Misconceptions
The Operation Flop
Adding a discount or subtracting a tax. Remind students: Sales = Lower, Tax = Higher.
Decimal Drifting
Changing 8% to 0.8 instead of 0.08. Watch for the 100-division step carefully.
Multi-Step Mix-up
Calculating tax on the original price in a discount scenario. Tax is almost always on the "Register Price".
Answer Key: Marketplace Math
Part 1: The Diner
Ticket #01: Tip = $5.85 | Total = $38.35
Ticket #02: Tax = $3.83 | Total = $48.83
Part 2: The Boutique
Parka: 180 × 0.35 = $63 off | New = $117
Shoes: 95 × 0.15 = $14.25 off | New = $80.75
Sunglasses: 42 × 0.60 = $25.20 off | New = $16.80
Part 3: Multi-Step Challenge
Step 1 (Discount): $400 × 0.20 = $80 off. Sale Price = $320.00.
Exit Ticket Answers
1. Sneakers: 85 × 0.30 = 25.50 off | Final = $59.50
2. Cafe: 22 × 0.20 = 4.40 tip | Total = $26.40
Spot the Mistake: Tax should be ADDED, not subtracted.
