Using Decimals in a Shopping Context

Warmup

Mai had $14.50. She spent $4.35 at the snack bar and $5.25 at the arcade.

Activity #1

Decimals in the Shopping Cart.

You are going to do some shopping. Your aim is to do the best estimate as you can about how much money you have spent. 

• Use the sliders to buy the items and then try to guess how much you have spent and type your answer in the “My Guess” box.​
• Check the “Hide/Show“ box to see the actual amount that you spent. ​
• Click the reset button to try again.

Activity #2

Work with a Budget.

You are planning a dinner party with a budget of $50 and a menu that consists of 1 main dish, 2 side dishes, and 1 dessert. There will be 8 guests at your party.

• Choose your menu items and decide on the quantities to buy so you stay on budget.
• If you choose meat, fish, or poultry for your main dish, plan to buy at least 0.5 pound per person.

• Answer the questions below.

(1.) What is the budget in $ per person?

(2.) Use the table to record your choices and estimated costs. Then find the estimated total cost and cost per person. See examples in the first two rows.

(3.) Is your estimated total close to your budget? If so, continue to the next question. If not, revise your menu choices until your estimated total is close to the budget.

(4.) Calculate the actual costs of the two most expensive items and add them. Show your reasoning.

(5). How will you know if your total cost for all menu items will or will not exceed your budget? Is there a way to predict this without adding all the exact costs? Explain your reasoning.

Activity #3

Work with Cash Register.

In the applet below, the maximum cost of an item is $1.00. Follow the instructions below to start.

• Check the remaining boxes to reveal the coins.
• You can change the coin sizes by using the “Adjust coin size” slider.
• Check the remaining boxes to reveal the coins.
• You can change the coin sizes by using the “Adjust coin size” slider.
• Click on . An item will pop up for you to buy,
• Drag coins onto the cash register to pay for it.
• When you are certain that you have paid the correct amount, click on “Show total”. The applet will show the total.
• Click and the computer will approve your answer.
• Then click “Start over” to purchase a new item. Every item is under a dollar.

Challenge #1

Challenge #2

Challenge #3