"...my daughter ... uses your nine's trick every time she has to multiply by nine. ..All of her friends and the kids in my homeschool use your nine's trick. I can't wait to tell them about the 11's... I want to thank you for the work you have done." Arlene Arp www.SoMuch2Learn.com
Multiplying by 9: The 9's Trick
Look at a clock and write down what time it is because in about 10 minutes you will know all the answers to 9 x any number between 0 - 10.
Here is the 9’s trick.
Let’s start with an easy one.
9 x 2 = 18
You know this because 9 + 9 = 18. Now look at the next one,
9 x 3 = 27
Notice the two answers above, 18 and 27. A funny thing about multiplying by 9 is that the 2 digits in the answer will always equal 9, when added together.
Look at 18, add those digits together, 1 + 8 = 9. Now look at the answer 27, 2 + 7 = 9. It’s like this all the way up to 9 x 10.
Another funny thing about multiplying by 9 is that the first number in the answer will always be 1 less than the number your are multiplying by, for example,
9 x 4 = 36
The first number in the answer is 3, which is one less than 4. And since the numbers in the answer always equal 9, think to yourself
3 + ? = 9.
3 + 6 = 9, so “6” must be the second digit in the answer.
9 x 4 = 36
Let’s try this trick with
9 x 2 =
1 less than 2 is 1, so that is the first digit in the answer..
9 x 2 = 1_
1 + ? = 9 the answer is 8, so that’s the second digit in the answer.
9 x 2 = 18
Let’s try 9 x 3 =
1 less than 3 is 2, so
9 x 3 = 2_
2 + ? = 9, so
9 x 3 = 27
You try one. 9 x 5 =
One less than 5 is…
How much more to make 9?
The answer is 9 x 5 = 45
What is the answer to 9 x 6 =
One less than 6 is…
5 + ? = 9.
That’s right, 54.
Quick, what is the answer to this one 9 x 7 = ?
Think to yourself, one less than 7 is 6, so that is the first digit. And 6 + 3 = 9, so 3 must be the second digit. The answer is 63.
It works for 9 x 8 = 72 and for 9 x 9.
What is the answer to 9 x 9?
One less than 9 is 8 and 8 + 1 = 9, so the answer must be 81.
It even works for 9 x 10. One less than 10 is 9 and 9 + 0 = 9, so the answer is 90.
Answer the following,
9 x 6 = 9 x 4 = 9 x 7 = 9 x 3 =
9 x 8 = 9 x 5 = 9 x 2 = 9 x 9 =
Did you get them all right? What time is it? How long did it take you to learn all of the 9’s? Send an email and let us know so we can post it on the testimonials page.
Answers: 54 36 63 27
72 45 18 81
If you got all the answers right in 10 minutes you just Learned Math Fast, now imagine if you read the whole book.
Try it yourself by completing this worksheet: Multiplying by 9's Worksheet
Here is the 9’s trick.
Let’s start with an easy one.
9 x 2 = 18
You know this because 9 + 9 = 18. Now look at the next one,
9 x 3 = 27
Notice the two answers above, 18 and 27. A funny thing about multiplying by 9 is that the 2 digits in the answer will always equal 9, when added together.
Look at 18, add those digits together, 1 + 8 = 9. Now look at the answer 27, 2 + 7 = 9. It’s like this all the way up to 9 x 10.
Another funny thing about multiplying by 9 is that the first number in the answer will always be 1 less than the number your are multiplying by, for example,
9 x 4 = 36
The first number in the answer is 3, which is one less than 4. And since the numbers in the answer always equal 9, think to yourself
3 + ? = 9.
3 + 6 = 9, so “6” must be the second digit in the answer.
9 x 4 = 36
Let’s try this trick with
9 x 2 =
1 less than 2 is 1, so that is the first digit in the answer..
9 x 2 = 1_
1 + ? = 9 the answer is 8, so that’s the second digit in the answer.
9 x 2 = 18
Let’s try 9 x 3 =
1 less than 3 is 2, so
9 x 3 = 2_
2 + ? = 9, so
9 x 3 = 27
You try one. 9 x 5 =
One less than 5 is…
How much more to make 9?
The answer is 9 x 5 = 45
What is the answer to 9 x 6 =
One less than 6 is…
5 + ? = 9.
That’s right, 54.
Quick, what is the answer to this one 9 x 7 = ?
Think to yourself, one less than 7 is 6, so that is the first digit. And 6 + 3 = 9, so 3 must be the second digit. The answer is 63.
It works for 9 x 8 = 72 and for 9 x 9.
What is the answer to 9 x 9?
One less than 9 is 8 and 8 + 1 = 9, so the answer must be 81.
It even works for 9 x 10. One less than 10 is 9 and 9 + 0 = 9, so the answer is 90.
Answer the following,
9 x 6 = 9 x 4 = 9 x 7 = 9 x 3 =
9 x 8 = 9 x 5 = 9 x 2 = 9 x 9 =
Did you get them all right? What time is it? How long did it take you to learn all of the 9’s? Send an email and let us know so we can post it on the testimonials page.
Answers: 54 36 63 27
72 45 18 81
If you got all the answers right in 10 minutes you just Learned Math Fast, now imagine if you read the whole book.
Try it yourself by completing this worksheet: Multiplying by 9's Worksheet