Hi! My name is Mathew.
That’s Math_ _ as is mathematics and _ _ _ _ ew as in you are going to learn some multiplication tricks.
Before I share the new tricks let’s just review some other things to remember when multiplying.
Remember 0 times anything is always equal to 0.
2X0=0
Now it’s your turn, quick! What is 4 X 0?
That’s right it’s 0, good job
Remember 1 times anything is always equal to the "anything."
1X6=6
Now it’s your turn, quick! What is 1 X 9?
Great work, you are correct it’s 9.
And of course you remember that 10 times anything is the "anything" with a 0 added at the end.
10 X 3 = 30
What is 10 X 5?
That’s right. It is 50.
Now here is a trick you can use to help you with the Times 9 multiplication table for 9 x 0 through 9 x 10.
First write down the table:
9X0= 9X1= 9X2= 9X3= 9X4= 9X5= 9X6= 9X7= 9X8= 9X9= 10 X 9 =
Next complete the table with the easy answers for Times 0, 1, and 10.
9 X 0 = 0 (0 times anything always equals 0). 9 X 1 = 9 (1 times anything always equals the anything). 9X2= 9X3= 9X4= 9X5= 9X6= 9X7= 9X8= 9X9= 10 X 9 = 90 (10 times anything equals the anything with 0 added to the end).
Simple enough, right?
Next, pretend you don’t know the answers to 9 X 2 through 9 X 9 and starting at the top (9 X 2) write the numbers 1 through 8 next to each.
9X0=0 9X1=9 9X2=1 9X3=2 9X4=3 9X5=4 9X6=5 9X7=6 9X8=7 9X9=8 10 X 9 = 90
That was easy. Now do the same thing but start at the bottom (9 x 9).
9X0=0 9X1=9 9 X 2 = 18 9 X 3 = 27 9 X 4 = 36 9 X 5 = 45 9 X 6 = 54 9 X 7 = 63 9 X 8 = 72 9 X 9 = 81 10 X 9 = 90
Success! You can easily write down the Times 9 multiplication table for 0 through 10.
Times 11 everybody. Yes, that is what I said.
TIMES 11, it’s SCARY!
Or is it?
First, look at 1-digit numbers multiplied by 11.
It is much like multiplying by 1 except there are two places in the answer. (One times anything is anything – or in this case anything-anything).
11 X 0 = 0 (Remember, 0 times anything is always 0). 11 X 1 = 11 11 X 2 = 22 11 X 3 = 33 11 X 4 = 44 11 X 5 = 55 11 X 6 = 66 11 X 7 = 77 11 X 8 = 88 11 X 9 = 99 Wow! That was easy. But can you easily multiply 2-digit numbers by 11?
Yes – And here is the trick!
These are big numbers but don’t get scared.
Let’s look at 11 X 15.
Take the number you want to multiply by 11 (in this case 15) and imagine a space between the 2-digits.
1_5
Now add the two numbers together.
1+5=6
If the answer is a single-digit (1, 2, 3, etc.) put the sum in the space to get your answer.
165
So … 11 X 15 = 165
Go ahead and try a few.
11 X 12 = The answer equals 1 (1+2) 2 or 132.
11 X 26 = The answer equals 2 (2+6) 6 or 286.
11 X 81 = The answer equals 8 (8+1) 1 or 891.
You didn’t know you were so smart, did you.
Oh-oh … What do you do if the numbers in the space add up to a two-digit number like 10 or 17?
Well it’s a little tricky … But not hard.
Let’s take a look at 11 X 77.
Imagine that space between the 7 and 7.
7_7
Add the two numbers together (7+7=14)
Put the second number into the space (in this case it is 4)
747
Then add the number 1 to the first number.
(7+1)47 … or
Let’s do a little more practice.
The challenge: 11 X 29 =?
2_9 2 (2+9) 9 2 (11) 9 Keep the second space number in the space and add 1 to the first number. (2+1)19 319
So … 11 X 29 = 319
Let’s do another great big one just for fun.
11 X 98 =?
9_8 9 (9+8) 8 9(17)8 Keep the second space number in the space and add 1 to the first number. (9+1)78 1078
So … 11 X 98 = 1078
Wow! You catch on fast.
With a little practice, you will be able to multiply 2-digit numbers by 11 in your head.
Practice and challenge your friends (or maybe your teacher) to a 2-digit times 11 contest.
