4.4: Better Buy 2
Look at the pictures below. Can you figure out which store sells 1 box of noodles for less? In this concept, we will learn how to calculate the unit price of items in order to figure out which store has the better buy.
Guidance
In order to figure out which item is the better buy, like in the question above, we can use the problem solving steps to help.
- Start by describing what you see the pictures.
- Next, figure out what your job is in this problem. In all of these problems your job will be to figure out which item is the better buy.
- Then, make a plan for how you will solve. In these problems, you will want to figure out the unit price of the item at each store. Then, figure out which unit price is less.
- Next, solve the problem.
- Finally, check to make sure that the unit price at the store you chose is lower.
Example A
Look at the picture below. Which store sells a gallon of milk for less? How much would it cost to buy 2 gallons of Milk at Mac's?
Solution:
We can use the problem solving steps to help us with the first question.
The second question was: how much would it cost to buy 2 gallons of Milk at Mac's? Since one gallon of milk at Mac's is $4, two gallons of milk at Mac's is $4+$4=$8.
Example B
Look at the picture below. Which store sells a bottle of water for less? How much would it cost to buy 3 bottles of water at Mac's?
Solution:
We can use the problem solving steps to help us with the first question.
The second question was: how much would it cost to buy 3 bottles of water at Mac's? Since one bottle of water at Mac's is $2, three bottles of water at Mac's is $2+$2 + $2=$6.
Example C
Look at the picture below. Which store sells a pound of onions for less? How much would it cost to buy 2 pounds of onions at Zac's?
Solution:
We can use the problem solving steps to help us with the first question.
The second question was: how much would it cost to buy 2 pounds of onions at Zac's? Since one pound of onions at Zac's is , 2 pounds of onions at Zac's is .
Concept Problem Revisited
Vocabulary
A unit price is the cost of one item. In this concept, we are given the overall price for multiple items and need to find the unit price in order to figure out which store has the better buy.
Guided Practice
Use the picture below for problems 1-3.
1. Which store sells 1 cactus plant or less?
2. How did you decide?
3. How much would it cost to buy 3 cactus plants at Mac’s?
Use the picture below for problems 4-6.
4. Which store sells 1 box of strawberries for less?
5. How did you decide?
6. How much would it cost to buy 4 boxes of strawberries at:
- Mac’s? ________________________________
- Zac’s? _________________________________
Answers:
1. Zac’s
2. Mac’s: 1 plant is $12. Zac’s: Since 3 plants cost $30, 1 plant is $10.
3. , or $36
4. Mac’s
5. Mac’s: 1 box is half of $6, or $3
- Zac’s: 1 sack is half of $8, or $4.
6. Mac’s: $12
- Zac’s: $16
Practice
Use the picture below for problems 1-4.
- Which store sells 1 sack of oranges for less?
- How did you decide?
- How much would it cost to buy 4 sacks of oranges at Mac's?
- How much would it cost to buy 4 sacks of oranges at Zac's?
Use the picture below for problems 5-8.
- Which store sells 1 carnation for less?
- How did you decide?
- How much would it cost to buy 12 carnations at Mac's?
- How much would it cost to buy 12 carnations at Zac's?
Image Attributions
Description
Learning Objectives
Students determine the unit price of an item at two different stores in order to figure out which store has the better buy. Students use problem solving steps to help them.