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F1.1 · Use past and current situations to inform financial decisions

Learn to use past and current situations to inform financial decisions through clear examples and targeted practice.

Ontario Grade 9 Mathematics

Financial Literacy

Ontario Grade 9 Mathematics — study topic F1.1

Financial decisions are choices about how to use money. You might decide whether to buy something now, wait, or choose another option. A useful decision considers both what is happening now and what has happened before. For example, if you know that a certain item often goes on sale, that past experience may help you decide whether today’s price is worth paying. Past experience is useful, but it does not guarantee what will happen next. This lesson practises using information carefully rather than guessing.

What you will learn

Use information from past situations and current prices or needs to make a financial decision.
Compare choices using the same time period and relevant costs.
Explain how new information could change a decision.

Start with the situation

Suppose you need a calculator for school. One shop has it today for CAD 32. You remember that the same model was on sale for CAD 25 last month. That past price is information, but it does not prove the sale will happen again soon.

First, identify the decision you need to make. Then gather information that matters: the current price, how soon you need the item, whether another suitable option is available, and what you know from past situations. A suitable option meets your need. A lower price is not helpful if the item does not do the job you need it to do.

A financial decision is not simply choosing the smallest number. It is choosing an option that fits your needs and uses the available information. You may have to act now, or you may have time to wait and compare.

State what you need to decide.
Separate known facts from guesses.
Use past experience as evidence, not as a promise.

Compare information fairly

Comparing choices means checking the same kinds of information for each one. If two options have different prices, ask whether both include the same item and whether there are extra costs. Extra costs are amounts you must pay in addition to the listed price. For example, a delivery charge may make an online purchase cost more than its displayed price.

Time matters too. A past sale price tells you what the item cost before, not what it costs now. If you need the item tomorrow, waiting for a possible sale may not be practical. If you do not need it soon, checking prices again could be reasonable. The decision depends on the current situation as well as the past information.

A simple comparison table can keep the facts clear. Write down only information you know. If you do not know whether a sale will return, record that as uncertain rather than treating it as a fact.

Compare the full cost, not just a displayed price.
Check that each option meets the same need.
Match the decision to the time available.

Use arithmetic to make the choice clearer

You can use subtraction to find how much more one price is than another. Subtraction compares two amounts. You can also use addition to combine a price with an extra cost. These are familiar number skills that help you describe the financial choice; the arithmetic does not decide what matters most to you.

For example, the calculator’s current price is CAD 32 and its remembered sale price was CAD 25. The difference is CAD 7. This tells you how much higher the current price is than the past sale price. It does not tell you when, or whether, the sale will happen again.

A useful way to organize your reasoning is: current cost, past information, timing, and need. Then state what you would choose and why. Your explanation should connect the information to the decision. You might say that you would buy now because you need the item immediately, or wait because you have a suitable item already and can check prices later.

\text{difference} = \text{current price} - \text{past price}

Use arithmetic to describe differences and extra costs.
Do not treat a past price as a guaranteed future price.
Give a reason that connects the facts to your choice.

Information for the bag decision

Information	What it tells us
CAD 48 today	Current price of one suitable bag
CAD 40 last year	A similar bag has cost less in the past
CAD 45 today	Current price of another suitable bag
Needed before next week	Waiting has a time risk; a future sale is not known

Worked example

Deciding whether to buy a school bag

A student needs a school bag before classes begin next week. A suitable bag costs CAD 48 today. The student remembers that a similar bag cost CAD 40 during a sale last year. Another suitable bag is available today for CAD 45. Which choice is reasonable, and what information supports it?

Identify the need and timing
The student needs a suitable bag before next week. Waiting for a sale may not work because there is no information showing when another sale will happen.
Compare current options
Both bags are suitable, and both can be bought now. The second option costs CAD 3 less than the first, so it is the lower current price, assuming there are no extra costs or other important differences.
$48 - 45 = 3$
Use the past information carefully
The past sale price of CAD 40 shows that a lower price has occurred before. It does not prove that the same price will be available before classes begin. Since the student needs a bag soon, the current CAD 45 option is a reasonable choice based on the known information.

Answer: Choose the suitable bag available today for CAD 45, provided there are no extra costs or important differences. It meets the need on time and costs less than the other current option.

Check: The CAD 40 price is from last year. It supports the idea that prices can vary, but it does not guarantee a future sale. The recommendation uses a known current price and the student’s deadline.

Common mistakes and how to avoid them

Assuming that because something was cheaper before, it will soon be cheaper again.

Correction: Treat the past price as information about the past. Look for current evidence before relying on a future price.

Choosing the lowest listed price without checking whether the item meets the need or has extra costs.

Correction: Check suitability and the full cost before comparing options.

Comparing one option’s current price with another option’s past price as if both were available now.

Correction: Label each amount as current or past, and compare current options when making a decision today.

Giving a choice without explaining the information behind it.

Correction: Name the relevant facts, such as current cost, timing, and past experience, then explain how they support your choice.

Lesson summary

Financial decisions use information to choose how to use money.
Past situations can help you think, but they do not guarantee what will happen next.
Compare current choices fairly, including relevant extra costs and whether each choice meets your need.
Consider timing, and explain how the facts support your decision.

Check your understanding

Question 1

A notebook costs CAD 6 today. You remember seeing it for CAD 5 last month, but you need it for class tomorrow. What is the most careful conclusion?

It will definitely cost CAD 5 tomorrow.
CAD 5 is a past price, while CAD 6 is the known current price.
The current price must be wrong because it is higher.
You should wait because a sale is certain.

Show answer and explanation

CAD 5 is a past price, while CAD 6 is the known current price.

The CAD 5 price is information about last month. It does not show that the notebook will be on sale tomorrow. The current known price is CAD 6, and the deadline matters.

Question 2

Two suitable lunch containers are available now. One costs CAD 14, and the other costs CAD 11. Neither has an extra cost. How much less does the second container cost?

CAD 2
CAD 3
CAD 11
CAD 25

Show answer and explanation

CAD 3

Subtract the lower price from the higher price:

14 - 11 = 3

. The second container costs CAD 3 less.

Question 3

Which statement uses past information most carefully?

A product was cheaper last year, so it will be cheaper next week.
A past price shows what the product cost then, but I need current information to know today’s cost.
A past price is always more useful than a current price.
If a price changed once, it cannot change again.

Show answer and explanation

A past price shows what the product cost then, but I need current information to know today’s cost.

A past price describes an earlier situation. Current information is needed to know the price now, and a past change does not guarantee what will happen later.

Key terms

Financial decision: A choice about how to use money.
Current price: The price being asked for now.
Past information: Information from an earlier situation, such as a price seen before.
Extra cost: An amount paid in addition to the listed price, such as a delivery charge.
Suitable option: A choice that meets the need being considered.

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Published by DoAssignment. This reviewed lesson follows Ontario Grade 9 Mathematics (MTH1W), expectation F1.1. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

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