Lesson 17

The warm-up reminds students of their understanding of percentage increase and decrease in preparation for the shares questions later in the lesson. Some students will use different strategies; identify those for the discussion after the activity.

Remind students that they can use any strategies from sixth grade for answering the percentages questions.

If students forget about using an equation to calculate percent increase or decrease, remind them that they can use the equation \(y=kx\) to figure out the answers to the questions.

The most important thing is to recall efficient methods of calculating percent increase and decrease, such as setting up an equation in the form A% of B is C. Select students to share their methods in preparation for the next activity.

Students are introduced to the idea of the stock market and how the value changes. They apply their understanding of negative numbers to percentage change as well as money (MP4). 

Introduce the concept of shares in a company. They have a specific value at a specific time that can change up or down. They represent a measure of the worth of the company. We sometimes express the change as a value in dollars, so investors can see how much money they will make or lose. We can also present these as a percentage to compare companies in terms of growth.

Before students begin working on the task consider asking how they would represent an increase or decrease in value so that it was easily apparent.

To familiarize students with the information in the table, consider asking which companies’ stocks increased in value and which companies’ stocks decreased in value from day 1 to day 2. Have students explain their reasoning and come to an agreement before anyone begins doing calculations.

The important part of this activity is that students use a directed quantity for percentage change to model decrease in value as negative and increase as positive. Ask students how they would prefer the information to be presented, and ask them to support their conclusions.

This task introduces the concept of a stock portfolio being a selection of stocks an investor might own to try to make money—students examine the change in portfolio and evaluate the value. They must use both positive and negative change, and percentage change.

Introduce the concept of a portfolio of shares in a company.

The important part of this activity is that it extends on the context previously examined, ahead of students building their own portfolio in a later activity.

Distribute copies of the "Stocks Prices"

Students calculate their own portfolio

Distribute copies of the "Changes in Stock Prices after 3 Months" so they can calculate the change.

Distribute copies of the Stock Prices Blackline Master. Have prepared the Changes in Stock Prices after 3 Months Blackline Master.

Have students trade with a partner and check each other's work. (Answers vary because each student worked with a different selection of stocks.)

Have students examine the "Changes in Stock Prices after 3 Months" page and discuss:

• How can you tell if the price of a stock increased or decreased from looking at this list?
• Which company's stock price increased or decreased by the most?
• Without doing any calculations, predict which company's stock price had the largest increase as a percentage of its starting value.
• Without doing any calculations, predict which company's stock price had the largest decrease as a percentage of its starting value.