Student Survive 2 Thrive: Math Flash Cards: Multiply by 11 (11 is the 2nd Factor)

Thursday, September 22, 2016

Math Flash Cards: Multiply by 11 (11 is the 2nd Factor)

These math flash cards feature multiplying by eleven. Many people find this multiplication set to be fairly easy to learn - I hope my hints help you to master this set!

Tips for Multiplying by 11

I think the easiest way to learn to multiply the numbers one through nine by 11 is to simply write the number you are multiplying by 11 twice. For example, to multiply 4 by 11, write 44. If you are multiplying 8 by 11, write 88.
For multiplying 10, 11, and 12 by eleven, an interesting pattern emerges that may be helpful. Look at the number that you are multiplying by 11. Write down the first and last digit of that number, leaving a space between the two digits. The middle digit is the sum of the two digits that you wrote. For example, when multiplying 10 by 11, write 1 and 0 and leave a space between them. Next, add 1 and 0 and write that number as the middle digit, giving an answer of 110. Here is another example: when looking at 11 X 12, write 1 and 2 and leave a space tween them. Next, add 1 and 2 and write that number at the middle digit, giving an answer of 132.
Another way to multiply by 11 is to add the other number to itself 11 times. It is easy to lose count using this method. For example, when multiplying 5 by 11, imagine having eleven 5s or 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 55. Here's another example: when multiplying 9 by 11, imagine having eleven 9s or 9 + 9 + 9 + 9 + 9 + 9 + 9 + 9 + 9 + 9 + 9 = 99.
It may be easier to skip count by eleven when multiplying by 11. Simply skip count by 11s the number of times that is equal to the number you are multiplying by eleven. For example, when multiplying three by eleven, count by 11s three times...11 - 22 - 33 to get an answer of 33. Here is another example: when multiplying seven by eleven, count by 11s seven times...11 - 22 - 33 - 44 - 55 - 66 - 77 for an answer of 77.

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