Learn how to find the best deals and save money!
🎯 What We'll Learn:
A unit rate tells us the cost for ONE item.
When you go shopping, prices can be confusing:
Which is the better deal?
To find out, we need to know the price for ONE bottle. That's the unit rate!
Unit Rate: The cost for ONE single item
We use unit rates to compare prices and find the better buy (the option that costs less per item).
To find the price per item, use this formula:
(This is the unit rate)
Problem: 6 apples cost $3
Find: How much does ONE apple cost?
Step 1: Write the formula
Total Price ÷ Number of Items
Step 2: Plug in the numbers
$3 ÷ 6 apples
Step 3: Calculate
$3 ÷ 6 = $0.50
Once we find the unit rate for each option, we can see which is the better buy!
The LOWER unit rate is the BETTER BUY
Lower price per item = Better deal = More savings! 💰
Option A
10 pencils for $2
Option B
15 pencils for $4
Let's find out! (See next slide for the solution)
$2 ÷ 10 pencils = $0.20 per pencil
$4 ÷ 15 pencils = $0.27 per pencil
(rounded to nearest cent)
Option A: $0.20 per pencil
Option B: $0.27 per pencil
$0.20 < $0.27
Option A:
$6 ÷ 8 juice boxes = $0.75 per juice box
Option B:
$8 ÷ 12 juice boxes = $0.67 per juice box
(rounded to nearest cent)
Compare:
$0.75 vs. $0.67
$0.67 < $0.75
Before looking at the solution, try to solve it yourself:
Option A:
$7 ÷ 5 candy bars = $1.40 per candy bar
Option B:
$4 ÷ 3 candy bars = $1.33 per candy bar
(rounded to nearest cent)
Compare:
$1.40 vs. $1.33
$1.33 < $1.40
Always write out your division problem. This helps you:
Always include what you're measuring!
Write: $0.50 per apple ✓
Not just: $0.50 ✗
Money amounts should have 2 decimal places.
If you get $0.6666..., round to $0.67
If you get $1.234, round to $1.23
Does your answer make sense?
If 10 items cost $5, each item should be less than $1. If you got $12, something went wrong!
Which package of cookies is the better buy?
Option A: $8 ÷ 20 cookies
= $0.40 per cookie
Option B: $5 ÷ 15 cookies
= $0.33 per cookie
(rounded from $0.3333...)
Compare: $0.40 vs. $0.33
Which is less? $0.33 < $0.40
The team needs new soccer balls. Which is the better deal?
Option A: $42 ÷ 6 soccer balls
= $7.00 per soccer ball
Option B: $30 ÷ 4 soccer balls
= $7.50 per soccer ball
Compare: $7.00 vs. $7.50
Which is less? $7.00 < $7.50
After practice, you want to buy sports drinks. Which is the better buy?
Option A: $9 ÷ 12 bottles
= $0.75 per bottle
Option B: $15 ÷ 18 bottles
= $0.83 per bottle
(rounded from $0.8333...)
Compare: $0.75 vs. $0.83
Which is less? $0.75 < $0.83
You need notebooks for school. Which is the better buy?
Option A: $12 ÷ 5 notebooks
= $2.40 per notebook
Option B: $20 ÷ 8 notebooks
= $2.50 per notebook
Compare: $2.40 vs. $2.50
Which is less? $2.40 < $2.50
You're shopping for apples. Which is the better buy?
Option A: $6 ÷ 10 apples
= $0.60 per apple
Option B: $12 ÷ 16 apples
= $0.75 per apple
Compare: $0.60 vs. $0.75
Which is less? $0.60 < $0.75
Your tennis coach needs to order tennis balls. Which is the better buy?
Option A: $18 ÷ 24 tennis balls
= $0.75 per tennis ball
Option B: $30 ÷ 36 tennis balls
= $0.83 per tennis ball
(rounded from $0.8333...)
Compare: $0.75 vs. $0.83
Which is less? $0.75 < $0.83
You're ordering pizza slices for a class party. Which is the better buy?
Option A: $28 ÷ 45 slices
= $0.62 per slice
(rounded from $0.6222...)
Option B: $35 ÷ 60 slices
= $0.58 per slice
(rounded from $0.5833...)
Compare: $0.62 vs. $0.58
Which is less? $0.58 < $0.62
The art teacher needs markers. Which is the better buy?
Option A: $24 ÷ 32 markers
= $0.75 per marker
Option B: $40 ÷ 48 markers
= $0.83 per marker
(rounded from $0.8333...)
Compare: $0.75 vs. $0.83
Which is less? $0.75 < $0.83
You're buying granola bars for lunches. Which is the better buy?
Option A: $22 ÷ 30 granola bars
= $0.73 per granola bar
(rounded from $0.7333...)
Option B: $38 ÷ 48 granola bars
= $0.79 per granola bar
(rounded from $0.7916...)
Compare: $0.73 vs. $0.79
Which is less? $0.73 < $0.79
You're buying water for a field trip. Which is the better buy?
Option A: $26 ÷ 40 water bottles
= $0.65 per water bottle
Option B: $44 ÷ 64 water bottles
= $0.69 per water bottle
(rounded from $0.6875)
Compare: $0.65 vs. $0.69
Which is less? $0.65 < $0.69
When answering a better buy problem, you should explain your thinking clearly. Here's a great format:
Problem: Which is the better buy - 10 pencils for $2 or 15 pencils for $4?
My Work:
Option A: $2 ÷ 10 = $0.20 per pencil
Option B: $4 ÷ 15 = $0.27 per pencil
My Answer:
Option A is the better buy because each pencil costs $0.20, which is less than $0.27. This means I save $0.07 per pencil by choosing Option A.
Understanding unit rates helps you make smart decisions every day:
Stores often show the "unit price" on price tags. This is the unit rate! It helps you compare different sizes and brands quickly.
Gas prices are shown as price per gallon. That's a unit rate! You can compare prices at different stations.
Which pizza is a better deal - small pizza with 6 slices for $12, or large pizza with 12 slices for $20? You can find out!
Families use unit rates all the time to save money and stay within their budget. Now you can help!
❌ Wrong thinking: "$5 is less than $8, so the $5 option must be better!"
✅ Correct thinking: "I need to find the price per item to compare fairly."
Remember: The option with the lower total price is NOT always the better buy!
❌ Wrong: 10 pencils ÷ $2 = 5 pencils per dollar
✅ Correct: $2 ÷ 10 pencils = $0.20 per pencil
Remember: Always divide price by number of items!
❌ Wrong: $0.8333333333
✅ Correct: $0.83
Remember: Round to the nearest cent (2 decimal places)!
❌ Wrong: Thinking the higher unit rate is better
✅ Correct: The LOWER unit rate is the better buy
Remember: Less money per item = Better deal!
The Three Steps:
1️⃣ Find unit rate for Option A
2️⃣ Find unit rate for Option B
3️⃣ Compare - choose the lower one!
Your family is buying backpacks for three children. Which store has the better buy?
Try to solve this completely on your own before checking the answer!
Step 1: Find unit rate for Store A
$72 ÷ 4 backpacks = $18.00 per backpack
Step 2: Find unit rate for Store B
$96 ÷ 6 backpacks = $16.00 per backpack
Step 3: Compare the unit rates
Store A: $18.00 per backpack
Store B: $16.00 per backpack
$16.00 < $18.00
You've completed Unit Rates & Better Buy Problems!
You can now:
Keep practicing, and you'll become even better at finding great deals! 🎯
💡 Challenge yourself: Next time you're shopping with family, try calculating unit rates and finding better buys!