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Level Three > Number and Algebra

# Cost of Living

Purpose:

This is a level 3 number activity from the Figure It Out theme series.

Achievement Objectives:

Achievement Objective: NA3-1: Use a range of additive and simple multiplicative strategies with whole numbers, fractions, decimals, and percentages.
AO elaboration and other teaching resources

Specific Learning Outcomes:

find fraction (half, quarter) of money amounts

multiply money amounts by 2 and 10

Required Resource Materials:
FIO, Level 3, Theme: Time Travel, Cost of Living, page 11
A calculator
Activity:

Discuss with the students the strategies that they could use to calculate first the cost of an item that increases by a factor of 10 and then the cost of an item that is one-quarter the price.
As the prices that the students will be working with involve decimals, the students need to practise and discuss multiplying decimals by 10. There is a high likelihood that the prices the students will be working with will lead to fractions of cents when halved and quartered. Discuss with students rounding prices to the nearest 5 cents.
A strategy that may be useful for finding a quarter of a price is by halving and then halving again.
Discuss question 4 with the students. They could investigate recent price trends in these products as well as changes in the population. The Statistics New Zealand website (www.stats.govt.nz) and the Consumers’ Institute may provide useful information. They might also like to investigate recent price trends (for example, the price 5 years ago compared with now) of appliances such as computers and cellphones.
This could lead to an interesting discussion about items that were used in the past, such as gas lamps or dial phones, and things that we use now that may or may not exist in the same form in the future, for example, cars, bicycles, computers, and televisions.
As an extension, you could ask the students to solve this problem:
“You buy a T-shirt, a hamburger, and a bag of lollies some time in the future. In total, these items cost \$14 more than they would in our time. How much does each item cost?” The students will probably solve this using trial and improvement. One possible answer is that the future prices are \$5 for a T-shirt, \$30 for a hamburger, and \$4 for a bag of lollies.
Statistics New Zealand carries out regular comparisons of the price change of goods in order to calculate the consumer price index (CPI). The students could investigate the CPI and find out what items are covered in the index.

#### Answers to Activity

1.–3. Answers will vary. Teacher to check
4. Answers will vary. There may be less land for cultivation, and a larger population will increase the demand for wood and fresh food. This increased demand may push up the prices.