# Multiplication and Money

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Team Digital
Multiplication and Money
CCSS.MATH.CONTENT.4.MD.A.2

## Multiplication and Money

What is money multiplication? Follow along as we learn more about how to multiply money and multi-digit multiplication with money. Below we will explore more about money and multiplying with decimal points.

## How to do Multiplication with Money

How do you multiply with money? Many people find the total cost of something by adding up money. But, you can use multiplication to count money in a more efficient way. You can multiply the cost of one item by how many people buy it. When you multiply money with decimal points it can be helpful to take out the decimal points while multiplying as whole numbers and then put them back in at the end. When multiplying money with decimal points, follow these steps:

Step # What to do
1 Start by setting up the equation.
2 Multiply as whole numbers.
3 Circle the digits to the right
of the decimal point.
4 Count the digits to the right
of the decimal point.
5 Put the dollar sign on.

## Multiplication with Money – Examples

Imagine you want to sell breakfast muffins .and one box costs $4.25. Five people want to buy a box of muffins, how much money will you make? Start by creating a multiplication equation, here it is four dollars and twenty-five cents times five. Next, multiply as whole numbers. four hundred twenty five times five equals two thousand one hundred twenty-five. Then, circle the digits to the right of the decimal point and put the decimal point back in. Finally, put the dollar sign on to find the cost! You will receive twenty-one dollars and twenty-five cents from selling your breakfast muffins. ## Multiplication with Money – Summary Remember multiplication of money works practically the same as multiplication operations with different items or just numbers. Just keep in mind that you need to add the dollar sign after writing the numbers. Let’s repeat the steps necessary for multiplication with money. • Start by setting up the equation. • Next, multiply as whole numbers. • After that, circle the digits to the right of the decimal point. • Then, count the digits to the right of the decimal point. • Finally, put the dollar sign on. At the end of the video, there are interactive exercises and worksheets for continued practice of multiplying whole numbers by decimals. ### TranscriptMultiplication and Money "Oh no, these tickets are too expensive." : "I know! Let's have a bake sale!" Zuri and Freddie are raising money to go to the adventure park. To help them know how much money they have earned, we can use "Multiplication and Money". Many people find the total by ADDING up money. But, you can use multiplication to count money in a more efficient way. Zuri and Freddie are selling four kinds of treats. Their first treat, the brownie box, costs five dollars and fifty cents. If eight people bought a box of brownies, how much money will Zuri and Freddie get? We COULD add the boxes like in repeated addition. OR, we can use multiplication by using the price for ONE box.... and the NUMBER of people who buy the boxes. When multiplying money start by creating an equation. Each box costs five dollars and fifty cents, if there are eight boxes, how much will Zuri and Freddie earn? Next take out the decimal point, we'll put it back in later. Now we want to solve the equation "five hundred fifty times eight". Then, multiply as if it were a whole number. "Five hundred fifty TIMES eight" equals four thousand four hundred. Next, let's put the decimal back in. There are two digits to the right of the decimal point. So, the solution ALSO needs two digits to the right of the decimal point. That is where we put the decimal point! Our new number will be forty-four decimal point zero zero. Zuri and Freddie will earn forty-four dollars for their brownies. They are also selling cookies! If each box costs them six dollars and forty-five cents, and seven people buy boxes, how much money will they earn? Remember, start by creating a multiplication equation. We can write "six dollars and forty-five cents times seven". Next, take out the decimal point and multiply as if they were whole numbers. "Six hundrerd forty-five TIMES seven" equals four thousand five hundred fifteen. Then, we can count the number of digits to the right of the decimal point... And put the decimal point back in. Our number will change to forty-five decimal point fifteen. Zuri and Freddie will earn forty-five dollars and fifteen cents from selling cookies. However, Zuri and Freddie are also selling cupcakes! If each box costs four dollars and twenty-five cents, and five people bought boxes, how much money will they have earned? Start with the equation, how can you set it up? Multiply "four dollars and twenty-five cents times five". Next multiply as if they were whole numbers, what did you get when you multiplied? "Four hundred twenty-five TIMES five" equals two thousand one hundred twenty-five. Then count the digits and find the decimal point. Here the decimal point will go two digits in from the right. Now we can read it as money! Zuri and Freddie will get twenty-one dollars and twenty-five cents. Finally Zuri and Freddie have cake pops! Try this one on your own. Each box of cake pops costs three dollars and seventy-five cents, and four people buy a box of cake pops. How much will Zuri and Freddie earn? Pause the video while you work on this problem. Zuri and Freddie will receive fifteen dollars. Before we see if Zuri and Freddie made enough money, let's summarize. When multiplying with money (...) Remember to start by creating an equation. Next, take the decimal point out and multiply as if the numbers were whole numbers. Then count the digits (...) And put the decimal point back in. Finally, put the dollar sign! I wonder if Freddie and Zuri earned enough to go to the Bee's Knees Adventure park? ## Multiplication and Money exercise Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Multiplication and Money. • ### Which items can this customer buy? Hints Check the number of boxes and how much one box is worth. Multiply these to find the total price. For example: If there were 4 boxes of cupcakes that each cost$5.00 we would find the total like this.

Solution

• two boxes of muffins
OR
If we multiply $2.00 by 3 we get$6.00.

If we multiply $3.00 by 2 we get$6.00.

• ### Which gift card does the customer need to use?

Hints

Remember you are solving $3.50 x 4. Take the decimal point out to help you, so it becomes 350 x 4. Try writing out the problem like this. Multiply the ones place first, then the tens then the hundreds. Don't forget to add the decimal point back in. Solution They should buy the gift card worth$14.00.

Here we can see how we got the answer.

• If we multiply 0 by 4 we get 0, so we write that in the ones place.
• We then multiply 5 by 4 which is 20, so we write 0 in the tens column and then carry the 2.
• Then we multiply the 3 by the 4, which is 12 and add the 2 to get 14, which we write below.
• Don't forget to add the decimal point back in. Count two places from the right as these two digits represent cents.
• We then get the answer $14.00. • ### Can you match the boxes to the price? Hints Look at how much one box costs and then multiply it by the number shown in each picture. For example, if we were figuring out how much two boxes of brownies cost, we would solve it like this. Don't forget to add on any numbers you have carried over. Solution Four boxes of brownies costs$11.00.

• We first multiplied 5 x 4 to get 20. We write 0 in the ones column then carry the 2 across.
• We then multiply 7 x 4 to get 28. We add the 2 to 28 to get 30. We write 0 in the tens column and carry the 3 across.
• Next we multiply 2 x 4 to get 8. We add the 3 to the 8 to get 11. We write 11 in the hundreds and thousands columns.
• We can then count two digits in from the right to find where the decimal point goes to represent the cents.
• Therefore the total cost is $11.00. _____________________________________________________ Using the same method: • Five boxes of chocolate chip cookies costs$9.25.
• Six boxes of lemon cake slices costs $19.20. • Three boxes of cake pops costs$11.70.
• ### What could be bought with each gift card?

Hints

Look at how much one box costs and then multiply it by the number shown.

If we saw a cookie and then x 3 we would need to solve $1.50 x 3 as shown below. Can you use your knowledge of multiplication and times tables to help you? Solution Here is an example of what we could get with each gift card. If we multiply the price of one box by the number shown in each picture we get the following answers: For the$6.00 gift card a customer could get:

• 3 boxes of chocolate cookies
• 2 boxes of doughnuts
For the $9.00 gift card a customer could get: • 3 boxes of doughnuts • 2 boxes of croissants For the$12.00 gift card a customer could get:
• 4 boxes of doughnuts
• 6 boxes of chocolate cookies

• ### How much does the customer need to pay?

Hints

Remember to start multiplying in the ones column then move to the tens and then the hundreds.

Don't forget to add any numbers you have carried over.

Solution

Here is the completed multiplication equation. The customer owes Freddie and Zuri $7.95. • We first multiplied 5 x 3 to get 15. We write 5 in the ones column then carry the 1 across. • We then multiply 6 x 3 to get 18. We add the 1 to 18 to get 19. We write 9 in the tens column and carry the 1 across. • Next we multiply 2 x 3 to get 6. We add the 1 to the 6 to get 7. We write 7 in the hundreds column. • We can then count two digits from the right to find where the decimal point goes. The decimal point goes between the 7 and 9. • Therefore the total cost is$7.95.
• ### Can you help order the boxes at the bakery?

Hints

Look at how much one box costs and then multiply it by the number shown.

For example, if we wanted to know the cost of three boxes of tarts, we would solve it like this.

Can you figure out the total price of each set of boxes using a pencil and paper first and then put them in order?

Solution

These are the correctly ordered items from cheapest to most expensive.

• Two boxes of cheesecake slices costs $8.30. • Four boxes of blondies costs$9.40.
• Six boxes of tarts costs $10.50. • Three boxes of apple pie slices costs$10.95.