Alternative to Memorizing Times TablesDate: 01/13/2004 at 19:09:56 From: Samantha Subject: how do you remember 12's in just one day How do you remember the 12's times table in just one day? I have to do a times test tommorow and I only have one minute. Date: 01/14/2004 at 10:14:23 From: Doctor Ian Subject: Re: how do you remember 12's in just one day Hi Samantha, In general, you can't memorize that many things in a single day, and have them stick. Memorization takes lots of repetition and practice. It's kind of like digging a hole--you have to do it one shovelful at a time. However, you don't always have to memorize every little thing. For example, I haven't really memorized my 12's, except for 12 * 12 = 144 because the rest of them are pretty easy to figure out when you need them. For the first few, you can just multiply the individual digits: 2 * 12 = 24 Double the 1, double the 2 3 * 12 = 36 Triple the 1, triple the 2 4 * 12 = 48 Quadruple the 1, quadruple the 2 Multiplying 10 by anything is easy--just add a zero at the end: 10 * 12 = 120 So 5 times 12 will be half that: 5 * 12 = half of 10 * 12 = half of 120 = 60 For 6 and 8, we can use doubling: 6 * 12 = twice 3 * 12 = twice 36 = 72 8 * 12 = twice 4 * 12 = twice 48 = 96 That leaves only 7, 9, and 11. And since each of them is just 12 from something we know, we don't really have to memorize those, either: 7 * 12 = 6 * 12, plus 12 = 72 plus 12 = 84 9 * 12 = 10 * 12, minus 12 = 120 minus 12 = 108 11 * 12 = 10 * 12, plus 12 = 120 plus 12 = 132 Also, if you're multiplying by a single digit, you can use the distributive property to turn one hard multiplication into two easy ones, e.g., 7 * 12 = 7 * (10 + 2) = 7*10 + 7*2 = 70 + 14 = 84 This works for _all_ of them, and although it's not as quick, it's a good backup strategy. While memorizing them probably gives you the fastest way to recall them when needed, practicing thinking about them like I just described is a nice alternative. It may be easier that way at first and it will help you not only to understand why the answers are what they are, it might even help you memorize them faster as you keep practicing. I hope this helps! Write back if you'd like to talk more about this, or anything else. - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/