Have you ever seen someone multiply huge numbers by 11, in their head, in a matter of seconds?
Curious how they do it?
~
Multiplication by 11 is easy! To multiply by a 2-digit number add the two digits and place the sum in between! 57 x 11 = 627 <-- you need to carry the 1!
This rule also works for 3 or 4 digit numbers as well as higher. The key to remember is to carry when needed.
~
Some examples :
237 x 11 =
25(2+3)10(3+7)TEN CARRIES7
Here, 2 and 7 are placed as the far ends of the number which will be our answer.
Next, we add the adjascent digits one after another, carrying when necessary.
After, placing 2 at the first digit's place, we add the first two adjascent numbers, this time it's 2 + 3 which equals 5. 5 will be our second digit.
Next, we continue the process with the next two, 3 and 7. 3 + 7 equals 10. This is the case where we must carry the ten over to the next digit place by adding 1 ( Refresh yourself on carrying rules if necessary, it's all you need to know) The 5 in hundreds place becomes 6 because of the 3+7 carry over.
Now our answer sequence is almost done. So far we have 260_
The zero is present because of remainder zero from the carry.
For our last digit, we just bring down the 7 from the original number just like we did for the first digit, 2.
Giving us the answer 2607.
~
Let's try something bigger, more impressive:
We will a 4 digit number.. let's say 7443
7(7+4=11(carry))(4+4=8 )(4+3=7)3
7 changes to 8 from carry
81873 is our answer after doing the basic arithmetic.
~
One more, let do a BIG one! One in the millions!
4,072,231 x 11
Remember your rules and it's just the same, just longer. Don't let the numbers scare you!
And like a genius you know the answer is..
44,794,541
~
Have fun with this and see how large you can go! It's a great way to work out your mind.
Thanks for listening~
Curious how they do it?
~
Multiplication by 11 is easy! To multiply by a 2-digit number add the two digits and place the sum in between! 57 x 11 = 627 <-- you need to carry the 1!
This rule also works for 3 or 4 digit numbers as well as higher. The key to remember is to carry when needed.
~
Some examples :
237 x 11 =
25(2+3)10(3+7)TEN CARRIES7
Here, 2 and 7 are placed as the far ends of the number which will be our answer.
Next, we add the adjascent digits one after another, carrying when necessary.
After, placing 2 at the first digit's place, we add the first two adjascent numbers, this time it's 2 + 3 which equals 5. 5 will be our second digit.
Next, we continue the process with the next two, 3 and 7. 3 + 7 equals 10. This is the case where we must carry the ten over to the next digit place by adding 1 ( Refresh yourself on carrying rules if necessary, it's all you need to know) The 5 in hundreds place becomes 6 because of the 3+7 carry over.
Now our answer sequence is almost done. So far we have 260_
The zero is present because of remainder zero from the carry.
For our last digit, we just bring down the 7 from the original number just like we did for the first digit, 2.
Giving us the answer 2607.
~
Let's try something bigger, more impressive:
We will a 4 digit number.. let's say 7443
7(7+4=11(carry))(4+4=8 )(4+3=7)3
7 changes to 8 from carry
81873 is our answer after doing the basic arithmetic.
~
One more, let do a BIG one! One in the millions!
4,072,231 x 11
Remember your rules and it's just the same, just longer. Don't let the numbers scare you!
And like a genius you know the answer is..
44,794,541
~
Have fun with this and see how large you can go! It's a great way to work out your mind.
Thanks for listening~
