Nothing gives children more confidence than being able to do math successfully. Of all the subjects, math is known as the "difficult one," wreaking havoc on many students' progress and causing tremendous grief for the parents of these suffering children. Yet armed with a few number tricks, these students grow in confidence toward mathematics and begin to experience success where little or none was enjoyed before.
Make Math Fun
A lot of effort is not required to learn some basic number properties and some multiplication "tricks" that will aid a student's progress in basic school math. Not only will this information bolster student confidence, but also provide an interesting glimpse into the amazing world of numbers and mathematics. Such a glimpse might very well serve as the lever to launch a student into a deeper appreciation for the subject. According to the National Council of Teachers of Mathematics (NCTM), making math fun is critical to a student's success in this subject. Parental involvement in their children's education and a positive attitude toward their children's success is critical as well.
What could be more fun than your children's learning some really cool number tricks and then seeing how easily they can manipulate numbers in their heads? Do you think they might start feeling differently about the subject? What if your son or daughter could easily multiply, for example, by 11 up to 99, let us say? How cool would that be and how much fun would they have knowing they could do this with 100% accuracy?
The Multiplication-by-11 Trick
The multiplication-by-11 trick is quite easy to learn. I have taught this to 7- and 8-year olds with much success. If you are curious, the trick lies in 11 being expressed as the sum 10 + 1. Thus, when we multiply a number by 11, we are actually multiplying by 10 and then 1 and adding the pieces together. For example, 11 x 13 is actually 10 x 13 and then 1 x 13. We then add the pieces which are 130 and 13 to get 143. The simplicity of this method lies in that multiplication by 10 requires that we only add a trailing 0 to the number we multiply; and multiplication by 1 gives us back the same number (1 is known as the multiplicative identity for this reason).
Here is how this trick works for all numbers from 1-99. For any number less than 10, to get the product of 11 and that number, simply double the digit of the number to be multiplied: thus 11 x 9 = 99 and 11 x 7 = 77. For numbers from 10 up through 99, if the two digits that make up the number to be multiplied sum to 9 or less, than simply add the digits together and place the result in the middle of the digits to get the result: thus 11 x 27 = 297 (2 + 7 = 9; 9 goes between 2 and 7) and 11 x 71 = 781 (7 + 1 = 8; 8 goes between the 7 and 1).
If the two digits of the number to be multiplied sum to 10 or more, do as above except carry a 1 to the 10's column of the number being multiplied, and place in the middle the 1's digit of the result of the sum. Let's clarify with an example: 11 x 74. Since 7 + 4 = 11, we carry a 1 to the 7 of 74, thus making it 8; we place the 1 of the 11 in the middle of 74, which has become 84 by virtue of such carrying, to get 814. Here is another example to make this perfectly clear: 11 x 39. Since 3 + 9 = 12, we carry a 1 to the 3 of 39 to get 49. We then insert the 2 of 12 between the 4 and 9 for the final result, which is
429. That is all there is to it.
With the information above, your child now has the tool to multiply any number from 1-99 by 11. What an impressive capability. Imagine how much confidence little Mikey or Sarah will have when being able to do this number feat; moreover, envision the fun they can have while honing their number skills and getting some good mental exercise as well. The results can only be positive.
So sit and teach this number trick to your kids today and watch the results achieved. Perhaps in September when the kids go back to school, they will go in with a different attitude, one replete with confidence toward math.
Sources
- National Council of Teachers of Mathematics. Web. July 2, 2011.
Joe Pagano - Joe is a prolific writer, author, poet, and linguist, who has published over 200 articles and several books on a broad array of ...
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