Multiplying a Two-Digit Number by a One-Digit Number

Instructor: Francine White

Francine has taught elementary school and is currently an elementary Math specialist. She has two Master's degrees: Curriculum and Instruction in Math K-14 and Educational Leadership

In this lesson, you will review what multiplication is and learn two methods for multiplying a two-digit number by a one-digit number: the area model and the traditional method. You can use both to practice your multiplication skills!

What Is Multiplication?

Multiplication is a quicker way of adding the same number multiple times. Since we are repeating the same number, multiplication is also called repeated addition. For example, say you have 7 friends with 13 gummy bears each and you want to find how many they have in total. Instead of adding 13 + 13 + 13 + 13 + 13 + 13 + 13, it's much faster to multiply 7 x 13 to find the answer. When we multiply two or more numbers, the answer is called the product.

In this lesson, we will talk about two ways that you can multiply a two-digit number by a one-digit number to find the product: the traditional method and the area method.

Using Traditional Multiplication

The traditional multiplication method is the way most people multiply numbers. This method involves writing the numbers vertically and lining them up by place value (the ones should be in the same column, the tens should be in the same column, and so on). Let's use traditional multiplication to find the answer to our gummy bear problem.

Start by writing the problem vertically:


trad_1


Now, multiply the digits in the ones column. So, we will multiply 3 ones by 7 ones. Since this equals 21 ones, the 1 goes in the ones column and the 2 is carried over--place it above the tens column to be added later (just like carrying over when adding!):


trad_2


Next, multiply 1 x 7 to get a product of 7. Don't forget to add the carried-over 2 to get a sum of 9. Write the 9 in the answer section beside the 1:


trad9


You've just found your product: 91.

Using the Area Model

It you're having trouble with the traditional method, there's a different way of finding the product of a two-digit number and a one-digit number. The area model uses boxes to help us visualize each step of the problem and see how the numbers contribute to the product. (It's also called the box method!)

Begin by drawing the area model box. Since our largest number is two digits, we will need to divide it into two columns. Divide it into a tens section (which should be larger to fit the larger product) and a ones section. Since the other number in the problem is one digit, we only need one row.


modelbox


To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account
Support