Consumer Math - Sixth Grade
Complete Notes & Formulas
1. Unit Prices
What is a Unit Price?
Unit Price = Price per ONE item
The cost of a single unit of a product
Unit Price Formula
Unit Price = Total Price ÷ Number of Units
Example: Find unit price of a 6-pack for $4.50
Unit Price = $4.50 ÷ 6
Unit Price = $0.75 per item
Answer: $0.75 per item
Why Unit Prices? They help you compare different sized packages to find the best deal!
2. Comparing Products Using Unit Prices
Rule
Lower Unit Price = Better Deal!
Example: Which is the better buy?
Option A: 12 pencils for $3.60
Option B: 20 pencils for $5.00
Option A:
Unit Price = $3.60 ÷ 12 = $0.30 per pencil
Option B:
Unit Price = $5.00 ÷ 20 = $0.25 per pencil
Compare: $0.30 vs $0.25
Answer: Option B is the better buy!
3. Unit Prices with Unit Conversions
When Units Are Different
Step 1: Convert both to the SAME unit
Step 2: Calculate unit prices
Step 3: Compare
Example: Compare juice prices
Option A: 1 gallon for $6.00
Option B: 2 quarts for $2.50
Step 1: Convert to same unit (quarts)
1 gallon = 4 quarts
Option A: 4 quarts for $6.00
Unit Price = $6.00 ÷ 4 = $1.50 per quart
Option B: 2 quarts for $2.50
Unit Price = $2.50 ÷ 2 = $1.25 per quart
Answer: Option B ($1.25/qt) is cheaper!
4. Sale Prices and Discounts
Discount Formula
Discount = Original Price × (Discount %/100)
Sale Price = Original Price − Discount
Quick Formula
Sale Price = Original Price × (1 − Discount %/100)
Example: 25% off a $80 jacket
Method 1:
Discount = $80 × 0.25 = $20
Sale Price = $80 − $20 = $60
Method 2 (Quick):
Sale Price = $80 × (1 − 0.25)
Sale Price = $80 × 0.75 = $60
Answer: $60
5. Finding the Original Price
Formula
Original Price = Sale Price ÷ (1 − Discount %/100)
Example: Sale price is $45 after 25% off. Find original price.
Sale Price = $45
Discount = 25% = 0.25
Original Price = $45 ÷ (1 − 0.25)
Original Price = $45 ÷ 0.75
Original Price = $60
Answer: $60
6. Which is the Better Coupon?
Types of Coupons
Type 1: Dollar amount off (e.g., $5 off)
Type 2: Percent off (e.g., 20% off)
Example: Which coupon saves more on a $40 item?
Coupon A: $8 off
Coupon B: 25% off
Coupon A:
You save: $8
You pay: $40 − $8 = $32
Coupon B:
You save: $40 × 0.25 = $10
You pay: $40 − $10 = $30
Answer: Coupon B (25% off) is better!
7. Calculating Tax, Tip, and Mark-up
Sales Tax Formula
Tax Amount = Price × (Tax Rate/100)
Total Cost = Price + Tax Amount
Example: Sales Tax (6% tax on $50)
Tax = $50 × 0.06 = $3.00
Total Cost = $50 + $3 = $53.00
Answer: $53.00
Tip Formula
Tip = Bill × (Tip %/100)
Total = Bill + Tip
Example: 15% tip on $40 meal
Tip = $40 × 0.15 = $6.00
Total = $40 + $6 = $46.00
Answer: $46.00
Mark-up Formula
Mark-up = Cost × (Mark-up %/100)
Selling Price = Cost + Mark-up
8. Simple Interest
Simple Interest Formula
I = P × R × T
or
I = (P × R × T) / 100
Variables
| Variable | Meaning |
|---|---|
| I | Interest (money earned or paid) |
| P | Principal (starting amount) |
| R | Rate (as a decimal or percent/100) |
| T | Time (in years) |
Total Amount Formula
Total Amount (A) = Principal (P) + Interest (I)
A = P(1 + RT)
Example: $1,000 at 5% for 3 years
Given:
P = $1,000
R = 5% = 0.05
T = 3 years
Calculate Interest:
I = P × R × T
I = $1,000 × 0.05 × 3
I = $150
Total Amount:
A = P + I
A = $1,000 + $150 = $1,150
Interest: $150 | Total: $1,150
Quick Reference: Consumer Math Formulas
| Concept | Formula |
|---|---|
| Unit Price | Total Price ÷ Number of Units |
| Discount Amount | Original Price × (Discount %/100) |
| Sale Price | Original Price − Discount |
| Sales Tax | Price × (Tax Rate/100) |
| Tip | Bill × (Tip %/100) |
| Simple Interest | I = P × R × T |
💡 Important Tips to Remember
✓ Lower unit price = Better deal
✓ Always convert to same units before comparing
✓ Discount lowers the price
✓ Tax and tip increase the price
✓ Sale Price = Original − Discount
✓ Convert percent to decimal: divide by 100
✓ Simple interest: I = PRT
✓ Time must be in years for simple interest
✓ Total Amount = Principal + Interest
✓ Always write $ symbol for money answers!
🧠 Memory Tricks & Strategies
Unit Price:
"Total over Number, find the price per one - that's how it's done!"
Discount:
"Percent off means multiply, then subtract to find what you'll buy!"
Sales Tax:
"Tax is added to the bill, multiply then add for the final till!"
Simple Interest:
"I = PRT - Principal, Rate, Time, that's the key!"
Comparing Coupons:
"Calculate what you'll pay each way, choose the lower price - that's the way!"
Tip Shortcut:
"10% tip is easy - move decimal left once, you see! Double it for 20%, that's plenty!"
Master Consumer Math! 💰 💳 📊
Remember: Smart shopping means comparing prices!