The 11 Rule !!

By: Chandrajeet jeet
Submitted: 2008-08-06 15:46:27
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Math is not as difficult as you see it. You can always make it easy by using some quick tips. Sometimes we do math mentally. Remember most of us use 10 Rule for calculating the multiples of 10’s. You all may 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.

 To multiply any two digit number by 11:

• For this example we want to multiply 63 by 11.
• Separate the two digits in you mind (6__3).
• Notice the blank between them!
• Add the 6 and the 3 together (6+3=9)
• Put the resulting 9 in the blank 693. That's it! 11 x 63=693

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 blank and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the blank 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!

The 11 Rule Expanded

You can directly write down the answer to any number multiplied by 11.

• Take for example the number 51236 X 11.
• First, write down the number with a zero in front of it.

051236

The zero is necessary so that the rules are simpler.

• Draw a line under the number.
• Bear with me on this one. It is simple if you work through it slowly. To do this, all you have to do this is "Add the neighbor". Look at the 6 in the "units" position of the number. Since there is no number to the right of it, you can't add to its "neighbor" so just write down 6 below the 6 in the units col.
• For the "tens" place, add the 3 to the its "neighbor" (the 6). Write the answer: 9 below the 3.
• For the "hundreds" place, add the 2 to the its "neighbor" (the 3). Write the answer: 5 below the 2.
• For the "thousands" place, add the 1 to the its "neighbor" (the 2). Write the answer: 3 below the 1.
• For the "ten-thousand" place, add the 5 to the its "neighbor" (the 1). Write the answer: 6 below the 5.
• For the "hundred-thousand" place, add the 0 to the its "neighbor" (the 5). Write the answer: 5 below the 0.
  That's it ... 11 X 051236 = 563596

Using these quick math tips will develop the student learning skills. This helps the students to learn concepts using variety of approaches. The 11 Rule is one among them. I hope you all enjoyed learning this new tip. Practice it on paper first!

Article source: Expert Articles