3 ms·
I meant that when you're doing say 987 * 659 you end with an entire page of lines and having to count up 9 groups of cross each > 40, for instance in the case o
by Avshalom 17y ago
I meant that when you're doing say 987 * 659 you end with an entire page of lines and having to count up 9 groups of cross each > 40, for instance in the case of the middle column: accurately count and add 81, 40, 42.
The method still works fine it just becomes a hassle with a lot of chance for mistake (miscounting mostly) and looks way less elegant.
I like it too though, I just wouldn't teach it to a kid and then tell him to do 98*79.
- RiderOfGiraffes 17y agoSorry, I deleted my comment because it took me a moment to realise what you were saying. Yes, you're right. Here's how I avoid the problem. When I've use this method as an adjunct I've put two lines with a circle around them then labelled the "bundle" with how many lines there are. That way I can "have lots of lines" without actually drawing them all. The diagrams look similar, the method clearly works, and when I have used it, it's led the students to try to work out why it works, occasionally with success. I've found it to be a useful extra tool for teaching these things. BTW, I'm not the person in the video, it's just that I know and have used this technique.
- Retric 17y agoI would like to mention to you that this is really just another way to visualize traditional multiplication. 999 x 999 results in adding stacks of 81's but with this method you add vertically then horizontally where the traditional method does horizontal then vertical. aka vertical then horizontal: (81 + 81 * 2 * 10 + 81 * 3 * 100 + 81* 2 *1000 + 81 * 1 *10000) Horizontal then vertical: 999 * 9 + 999 * 90 + 999 * 900 = (81 + 810 + 8100) + (81 + 810 + 8100) *10 + (81 + 810 + 8100) * 100 If you chose diffrent groupings you can merge the two.