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Multiplication  Unique Timetable Patterns  5sAfter the basic concepts of multiplication have been taught, here are some tips to learning and memorizing multiplication facts for 5’s. The five timetables are generally easily learned, but here are some patterns that may help some struggling students. 5’s  Use skip counting to learn the 5’s. For instance, to calculate 5 x 4, count by 5’s four times…5, 10, 15, 20. Therefore, 5 x 4 = 20. Another consideration especially for older students: Take a look at the 2nd factor in the 5 timetables and the answer (product). Do you see a pattern? 5 x 1 = 05 (odd) 5 x 2 = 10 (even) 5 x 3 = 15 (odd) 5 x 4 = 20 (even) 5 x 5 = 25 (odd) 5 x 6 =30 (even) and so on Multiplying 5 by an EVEN factor: The first digit in the product is half of the 2nd factor without a remainder or with nothing left over. So, the second digit in the answer is 0. Example, 5 x 4 = 20  two is half of 4; add a zero behind it. By the way, half of a number is the same as dividing by 2. Will this work for 5 x 8 ? Half of 8 is 4; add a zero to the end  5 x 8 = 40. Count by 5’s eight times to check for accuracy. 5, 10, 15, 20, 25, 30, 35, 40. Yes! It works! Multiplying 5 by an Odd factor: Odd numbers don’t divide in half evenly. There will be a remainder. So, subtract 1 to get an even number; then take half. Next, add a 5 behind the number. I’ll tell you why later. Example: 5 x 3 Step 1 – subtract 1 from 3 (31=2) Step 2  Take half of two (1) Step 3  Add a five behind the ‘1’ (15) 5 x 3 = 15 Another example: 5 x 7 Step 1 – subtract 1 from 7 (7 – 1 = 6) Step 2  Take half of six  (3) Step 3  Add a five behind the ‘3’ (35) 5 x 7 = 35 Note: I’m able to remember to add a 5 behind the number because I noticed another pattern. If I imagine a decimal between the digits of the product, the result is exactly half of the number being multiplied by 5. Check it out with a calculator for 5 x 7! Enter “ 7 / 2 “ ; the result is 3.5 Hmmm, 5 x 7 = 35 Have fun testing the others. ****Remember the COMMUTATIVE PROPERTY – the order of the numbers does not change the answer. One fact learned means that two facts are actually learned. Example: 4 x 5 = 20 and 5 x 4 = 20 If you would like an interactive learning tool, consider Hot Dots Multiplication Flash Cards. A special pen is used to select an answer. A correct answer will produce a bright light and sound, and a wrong answer gives a “bong” sound. This is the version I used in my class without any groans. However, now there is a new and improved pen with new sound effects, lights, and it talks. . Keep in mind, the pen is sold separately, and you can choose whether you want to hear words and/or sounds on the pen. That’s good to know for a classroom setting.
Content copyright © 2013 by Beverly Mackie. All rights reserved.
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