Friend Linda Lewis sent this interesting note:

“This year we will experience 4 unusual dates …. 1/1/11, 1/11/11, 11/1/11, 11/11/11.

 

Now go figure this out. Take the last 2 digits of the year you were born plus the age you will be THIS year and it WILL EQUAL 111.”

Thanks, Linda!  That’s cool.

I wish I knew why it works.  If you know the magic behind it, please explain it in a comment.

The number 11 is a prime number – not divisible by anything except itself or the number 1.  That’s all I know about this odd number except the easy way you can multiply with it. For doing it here’s a handy little instruction I snapped off the internet.

The 11 Rule

You likely know the 10 rule (to multiply by 10, just add a 0 behind the number) but do you know the 11 rule? It is as easy! You should be able to do this one in you head for any two digit number. Practice it on paper first!

To multiply any two digit number by 11:

• For this example we will use 54.
• Separate the two digits in your mind (5__4).
• Notice the hole between them!
• Add the 5 and the 4 together (5+4=9)
• Put the resulting 9 in the hole 594. That’s it! 11 x 54=594

The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the “ones” digit in the hole and carry the “tens” digit from the addition. For example 11 x 57 … 5__7 … 5+7=12 … put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 … 11 x 57 = 627
Practice it on paper first!

Finally, while you’re manipulating elevens, how about a little card trick? I was looking for one that involves the number 11, but this one looked like fun.

Before you watch the video tutorial, have a deck of cards handy.  During the steps, you’ll use – not 11 – but 9 of them.