Dubai Forums Dubai Discussions Dubai General Chat

I wonder if this it true? It's certainly an easy way to do it for people who find maths hard (and don't have a calculator).

I tried 1340 x 24 and after one false start I got the right answer.

http://www.youtube.com/watch?v=FJdxa8KP ... annel_page

Well groovy!

Oh man, I though it was going to be a racist joke.


But seriously, it's a pretty cool trick but the examples he gives are all low numbers. What bout 989 x 789? That's a lot of lines.

I bet I you could do it easier and quicker using the 'normal' multiplication techniques.

You're right, I tried it, took 4 minutes just to draw the lines and work out the number of intersecting points. The numbers didn't make sense, need more instruction on how you carry over the double and triple digits. It may work but long-winded to say the least.

Then tried same sum the old fashioned way. I haven't done long multiplication with a pen and paper in 20 years, got the right answer in just over a minute.

Chinese Schminese.

Richard Head wrote:You're right, I tried it, took 4 minutes just to draw the lines and work out the number of intersecting points. The numbers didn't make sense, need more instruction on how you carry over the double and triple digits. It may work but long-winded to say the least.

Then tried same sum the old fashioned way. I haven't done long multiplication with a pen and paper in 20 years, got the right answer in just over a minute.

Chinese Schminese.

I just read that and was like "pfff, a minute? How slow are you?" Then I tried it and got the wrong answer. ha!

Second time around I got it right.

Well now you got me started, love a challenge. try 937 x 819, watched the clock a bit more closely this time. 34 seconds to beat, right first time

Yep neat trick but that's all I guess. Plus it doesn't teach you anything about numbers - units, tens, hundreds, etc. and how to group them for quick mental maths.

This is more likely:

http://mathforum.org/kb/message.jspa?messageID=6692551
I like how the Chinese kids are taught, at least as Liping Ma claimed they are taught. She says that in the fourth grade, as soon as they are taught fractions, they are taught that dividing by a number is equivalent to multiplying by that number's reciprocal, that a/b = a(1/b). And so when it's time to learn division of rational numbers (fractions), since they are already taught that the reciprocal of c/d can be written as 1/(c/d) or (d/c), they have a ready made application: (a/b)/(c/d) = (a/b)[(1/(c/d)] = (a/b)(d/c).


This lady Liping Ma seems to be setting a fire under US maths teaching:

http://rationalmathed.blogspot.com/2007 ... y-say.html

http://www.scienceblog.com/community/ol ... b0668.html

Richard Head wrote:Well now you got me started, love a challenge. try 937 x 819, watched the clock a bit more closely this time. 34 seconds to beat, right first time

65 seconds, second time around. *puts gun to head*

God and I have an engineering degree. I blame computers.