Finding the Better Buy
Finding the better buy means comparing two or more products by calculating each unit price and choosing the one with the lower cost per unit. For example, Brand A soda at 4 dollars for 80 oz costs 0.05 dollars per ounce, while Brand B at 3 dollars for 50 oz costs 0.06 dollars per ounce, making Brand A the better buy. This practical consumer math skill is covered in Chapter 6 of Saxon Math Course 2 for 7th grade math and applies ratio reasoning to real-world shopping decisions.
Key Concepts
Property To compare products, calculate the unit price for each one. The item with the lower unit price is the better value. $$ \text{Unit Price} = \frac{\text{Total Cost}}{\text{Quantity}} $$.
Examples Brand A soda is 4 dollars for 80 oz. Unit price: $\frac{4 \text{ dollars}}{80 \text{ oz}} = 0.05$ dollars per oz. Brand B is 3 dollars for 50 oz. Unit price: $\frac{3 \text{ dollars}}{50 \text{ oz}} = 0.06$ dollars per oz. Brand A is the better buy. A 10 ounce bag of chips costs 4.50 dollars (0.45 dollars/oz). A 16 ounce bag costs 6.40 dollars (0.40 dollars/oz). The 16 ounce bag is the better buy.
Explanation Don't let big packages trick you! To find the real bargain, be a smart shopper and find the price for just ONE unit (like one ounce or one can). The item with the smallest single unit price is your winner, saving you money in the long run.
Common Questions
How do you find the better buy in math?
Calculate the unit price for each option by dividing the total cost by the quantity. Compare the unit prices and choose the lower one. For example, 4 dollars / 80 oz = 0.05 per oz vs 3 dollars / 50 oz = 0.06 per oz. The first is the better buy.
What is unit price and why does it matter?
Unit price is the cost per single unit of a product. It matters because products come in different sizes at different prices. A larger package might look more expensive but actually cost less per unit, making it the better value.
How do you compare prices of different sized products?
Convert both to the same unit measurement by calculating unit price. Divide each products total price by its quantity to find the cost per ounce, per item, or per pound. The product with the lower unit price is the better deal.
Is the bigger size always the better buy?
Not always. While larger packages often have lower unit prices, this is not guaranteed. You must calculate and compare unit prices. Sometimes smaller sizes are on sale and offer a better per-unit value.
What is a real-world example of finding the better buy?
At a grocery store, a 12-oz bag of chips costs 3.60 dollars (0.30 per oz) and a 16-oz bag costs 4.48 dollars (0.28 per oz). The 16-oz bag is the better buy because it costs 2 cents less per ounce.
When do students learn about finding the better buy?
This skill is taught in 7th grade math as part of ratio and proportional reasoning. Saxon Math Course 2 covers it in Chapter 6, where students practice calculating unit prices and comparing values in consumer math scenarios.