Multiplication: 2-digit by 2-digit

Contributor: Ashley Nail. Lesson ID: 13184

Can math make you hungry? Use two methods to solve multiplication problems and determine the most successful food truck at a festival. Then, create your own food truck!

categories

Elementary, Numbers & Operations

subject
Math
learning style
Kinesthetic, Visual
personality style
Otter, Beaver
Grade Level
Intermediate (3-5)
Lesson Type
Quick Query

Lesson Plan - Get It!

Audio:

Have you ever been to a food truck festival? There are normally a lot of food trucks serving many different kinds of food. You may see long lines at some trucks and shorter lines at others. Also, each food truck has its own menu with different prices.

Watch Toronto Food Truck Festival is the city's huge food truck festival from blogTO to see an example:

 

Wow! So many food trucks with so many different kinds of food.

  • But how can you tell which food truck is making the most money at the festival?

High prices and long lines may not give the answer away! We're going to use multiplication to find out which food truck has the perfect combination of "just right" prices and number of customers!

Let's imagine that we own a food truck named the Roving Rolling Meatball, and we serve meatball sub sandwiches! Our specialty drink is an Italian soda, and our side dish is spaghetti.

meatball sandwich

The food truck festival is packed full of people, and every food truck has a long line! I wonder which food truck makes the most money per hour?

On average, our food truck takes 59 orders an hour. A full order, which includes a drink, entree, and side, is $23.

  • How much money does our food truck make an hour?

The best way to solve this problem is multiplication!

We can multiply 59 times $23 to get the total amount of money our food truck will make in an hour. We will set up our equation like this:

equation

We can solve this multiplication problem two ways! First, we will use an area model.

In order to use an area model, we need to break down 59 into 50 and 9. We will break $23 into $20 and $3.

   

50

9

 

$20

   
 

$3

   

 

Now, we will fill in the boxes of our area model. The first box represents the product of $20 x 50.

   

50

9

 

$20

$20 x 50 = $1,000

 
 

$3

   

 

Next, we will move across the top of the box and multiply $20 by 9.

   

50

9

 

$20

$20 x 50 = $1,000

$20 x 9 = $180

 

$3

   

 

  • Can you guess what we will multiply next?

If you thought $3 x 50, you were right! Last, we will fill in the final box with the product of $3 x 9.

   

50

9

 

$20

$20 x 50 = $1,000

$20 x 9 = $180

 

$3

$3 x 50 = $150

$3 x 9 = $27

 

The last step to find out how much money our food truck makes in an hour is to add together the products from each box!

$1,000 + $180 + $150 + $27 = $1,357

So, now we know 59 x $23 = $1,357. The Roving Rolling Meatball food truck makes $1,357 an hour!

Let's double check our answer by solving the multiplication problem using the standard algorithm.

This time, we set up our equation by writing the factors on top of each other. We also make sure to line up the digits so that the ones and tens are in line.

      hundreds tens ones
         

5

9

 

x

$

   

2

3

             

 

First, we multiply 3 x 9. We know the answer is 27, but we can only write one digit in the ones place. So, we will write the 7 under the line and carry the 2 to the tens place. The 2 will be added in the next step.

          +2  
         

5

9

 

x

$

   

2

3

           

7

 

Next, we multiply 3 x 5 which is 15. But, don't forget the 2! We add the 2 we carried over to 15. So, 15 + 2 = 17. Now, we can write 17 below the line. And don't forget to bring down the $ sign!

          +2      
         

5

9

 

3 x 5 = 15

 

x

$

   

2

3

 

15 + 2 = 17

   

$

 

1

7

7

   

 

Remember when we used an area model and we broke 23 into 20 and 3 and then used those numbers to multiply? Well, we are actually doing the same thing when we use the standard algorithm! We just finished multiplying 59 by 3 and now we are ready to move on to multiplying by 20. To show this, we are going to write a 0 in the ones place below the line and below the first product we found.

                 
         

5

9

   
 

x

$

   

2

3

   
   

$

 

1

7

7

   
           

0

   

 

Now, we will multiply 2 x 9, which is 18. We will write the 8 below the line and next to the 0. We will carry the 1 and add it next.

          +1      
         

5

9

   
 

x

$

   

2

3

 

2 x 9 = 18

   

$

 

1

7

7

   
         

8

0

   

 

Next, we multiply 2 x 5 which is 10. Don't forget to add the 1 from the last step. We write this answer below the line and bring down the $ sign.

          +1      
         

5

9

 

2 x 5 = 10

 

x

$

   

2

3

 

10 + 1 = 11

   

$

 

1

7

7

   
   

$

1

1

8

0

   

 

Lastly, we will add our products below the line to find the final answer!

             
         

5

9

 

x

$

   

2

3

   

$

 

1

7

7

 

+

$

1

1

8

0

   

$

1

3

5

7

 

59 x $23 = $1,357. We solved for the same answer again! The Roving Rolling Meatball makes $1,357 per hour!

I still wonder which food truck makes the most money in an hour. Let's move on to the Got It? section to see how much money other food trucks make!

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