Copyright

How to Multiply by 9

Instructor: Christine Quist

Christine has taught 4th-5th grade, has worked as a Paraprofessional for Adult Learners, and has a master's degree in Curriculum and Instruction for Elementary Education.

In this lesson, you will learn how to multiply by 9. First you will use a magic trick done on your hands. Then you will solve a story problem to practice multiplying larger numbers by 9.

Multiplying by 9

You might think that multiplying by 9 sounds tricky, but it is actually the same as multiplying by 8, 2, or even 500! It is a way of skip counting by the amount of 9. For example, 9 x 3 = 27, which is the same as 9 + 9 + 9.

To help you memorize the early facts, you will first learn a trick for the nine times table. Then you will get a chance to solve a fun story problem to practice your understanding.

Magic Nines Trick

Magic Nines

Hold your hands out in front of you, palms down, so you can see all ten fingers like in the picture. To do 9 x 2, you will need to put down your second finger, the finger next to your left hand pinky. The finger that is folded down is going to show place value. Everything to the left of the tucked finger will be in the tens place, and everything to the right will be in the ones place. With the second finger down, we have 1 on the left side (10) and 8 on the right side, which means our answer would be 18! So, 9 x 2 = 18.

You can use this method to go all the way up to 9 x 10! Put down that tenth finger on your right hand, and what do you have? 9 fingers on the left side and 0 on the right! So, 9 x 10 = 90.

Next time you have a few minutes to spare, practice your Magic Nines, and you will soon have them memorized!

Story Problem

Let's pretend you are the captain of the Jolly Nine ship, and you have 9 pirate penguins who each need 24 gold pieces for the pirate penguin pay day. How many gold coins do you need to count out of the treasure chest to make sure each pirate gets paid equally?

Pirate Penguin Gold

First, let's set up the problem. We are multiplying the amount of penguins by the amount of golden coins each of them will get. So, the problem will be 9 x 24. On paper, let's put the 24 on the top, the 9 below the four, and the little x showing that we are multiplying on the left side like in the picture below.

24x9

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 200 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