Shopping for Savings

Purpose

This unit involves students in calculating savings and finding the best value items from a list of products. It would ideally be carried out prior to a school camp or similar, with students given the challenge of finding the best bargains for the trip.

Specific Learning Outcomes
  • calculate amount saved from given prices and percentage savings
  • identify the best value item from a list of similar grocery items
  • check the reasonableness of answers obtained using a calculator
Description of Mathematics

This unit involves students in calculating savings and finding the best value items from a list of products. It is suitable for students working at Stages 7-8, Advanced Multiplicative-Advanced Proportional, of the Number Framework. Students working at these levels use a range of multiplication and division strategies to estimate answers and solve problems with fractions, proportions and ratios.
Calculators are included in this unit as tools for calculation, with the students required to be able to justify the reasonableness of answers obtained.

Required Resource Materials

Copymaster 2

Copymaster 3

Calculators

Supermarket receipts containing items that have been reduced in price

Paper and pencils for working

A selection of grocery advertising flyers or access to online information about special prices

Copymaster 1

Copymaster 4

Computer with internet access

Copymaster 5

Activity

Station One

  • Copymaster 1
  • Paper and pencils for working
  • Calculators

Station Two

  • Supermarket receipts containing items that have been reduced in price
  • Copymaster 2
  • Paper and pencils for working
  • Calculators

Station Three

  • Copymaster 3
  • Paper and pencils for working
  • Calculators

Station Four

  • A selection of grocery advertising flyers or access to online information about special prices
  • Copymaster 4
  • Paper and pencils for working
  • Calculators

Station Five

  • Computer with internet access
  • Copymaster 5
  • Paper and pencils for working
  • Calculators

Additional activities for students to practice and consolidate skills in calculating percentage problems can be found in the Material Masters. Masters 8-21, 8-32 and 8-33 would be suitable for this purpose. Material Master 7-5 contains a game for students based around calculating percentages that may also be useful.

Stations

This unit is presented as a series of five activities, or stations, based around the same theme. If appropriate your whole class could rotate around these stations over the course of a week. Alternatively, the activities could be given to the groups of students working at the Stage 7-8 level in your class and others given alternative work as part of the classroom programme.

Station One

At this station students practice calculating reduced prices from initial prices and percentage reductions.
You will need to support students as they work through this task. You could either complete the first few examples with them, or give them a chance to try on their own before you check progress. Ensure students understand the difference between the two price options at the different supermarkets and help them to compare these in a logical way.

Students can use a calculator to help but tell them they need to be able to justify the reasonableness of answers obtained.

Copymaster 1 contains problem sets for students to work through.

Station Two

At this station students use supermarket receipts to calculate percentage reductions on sale items and an overall percentage saved. Help students identify the items on the receipts that were on special when purchased and find the original price and the amount saved for these items. Once these numbers have been found students use these numbers to calculate the percentage reduction for each item on special. You may need to help with the first few examples.

Students can use a calculator to help but tell them they need to be able to justify the reasonableness of answers obtained.

Once all items on special have been found, students calculate the total amount saved and the total amount spent. This can be done in two ways, either calculating a percentage saved on just the items on special, or the percentage saved on the supermarket bill overall. If time allows have students do both calculations to enable comparison. Discuss how choosing items on special increases the percentage saved but often percentage savings is not the only consideration when shopping.

Copymaster 2 contains instructions for students.

Note: Not all supermarkets present information on receipts in this way. New World and Countdown are two supermarkets that do indicate items purchased on special.

Station Three

Students participate in the ten dollar challenge. Working from a list of grocery items and their prices the challenge is to spend a total less than $10 on any selection of items while making the biggest savings possible. They can use a calculator to help but tell them they need to be able to justify the reasonableness of answers obtained.

Copymaster 3 contains this activity.

To complete this task, students will first need to calculate the reduced price and the amount saved for each item. Support students in this as required. Once this is done discuss with students the strategies they might use to solve this problem. These might include:

  • Trial and error, experimenting with different combinations of items to maximize savings.
  • Selecting the maximum number of items with the highest percentage saving possible.

Encourage students to discuss the strategies they are using as well as the answers they come up with?

 How did you choose those items?
Why did you do it that way?

Station Four

At this station students use a collection of grocery advertising flyers to make a list of all drinks on special and then work out which drink is the best value in terms of cost per litre of drink. They can use a calculator to help but tell them they need to be able to justify the reasonableness of answers obtained.

Copymaster 4 contains this activity.

Once students have listed the drinks and identified the price per litre, ask them to look at the problem another way. For each drink, how many litres are being purchased per dollar spent? Either way of looking at it will identify the better value products but the cost per litre is easier to calculate mentally as you do the shopping. Why? (The number of litres is usually a whole number and the number of dollars usually isn’t so it’s easier to divide by the number of litres than the number of dollars).

As alternative to using flyers, students could access information about prices of drinks through supermarket websites.

Station Five

At this station students use online shopping sites to look for the best value items. 

Students can use either the browse or the quick-list functions on these sites. Full information on using these features this can be found online.

Students find the items they are looking for and evaluate the products displayed to find the best value. To compare products students will need to calculate the cost per kg, g or litre as appropriate for each item and may need some support to do this.

Encourage students to use a calculator but tell them they need to be able to justify the reasonableness of answers obtained. For example, if calculating the cost per litre of juice when 3 litres costs $5.90, it is reasonable to use the strategy of tidy numbers and round the $5.90 up to $6.00. This makes the calculation 6 ÷ 3 which is a much simpler problem. Using this strategy, students can estimate the cost per litre to roughly $2.00.

How do you know that is the right answer?
What simpler calculation could you use to check?

Have students make a list of the items they have selected, including brand name, and the price for these as they work so they can calculate the total price when finished.

Copymaster 5 contains student instructions for this task.


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