10 Easy Math Tricks You Probably Don't Know

re: 10 Easy Math Tricks You Probably Don't Know

rosepotl — Sun, 24 Feb 2008 23:03:01 GMT

Math just got harder than ever!

re: 10 Easy Math Tricks You Probably Don't Know

LadyPam — Mon, 18 Feb 2008 13:31:23 GMT

Are the purist teachers seriously suggesting we insist every child work out EVERY multiplication by means of lining up counters in square formations?

Neither approach is sufficient on its own. Take language as an analogy: Children begin speaking by rote, by copying simple words/phrases that get them the desired result. It would be ludicrous to suggest that they should be made to study grammar, punctuation, comparative philology and the mechanics of voice/speech production before being permitted to communicate.

In my earliest schooldays, we learnt tables by rote. Then I moved schools at age 8 and found we were being taught new mathematics. I think Nuffield but it was a LONG time ago. Multiplication tables were outlawed and we were forbidden to learn any formula. Everything had to be figured out from basic principles every time. Imagine being forbidden to mutter to yourself "pi r squared" when useful. Luckily, before reaching O-levels (in those days), I moved schools again and was allowed to use formulae.

One school system has children learning times-tables by rote in early years, and has them speaking, singing and playing in foreign languages, all BEFORE learning to read/write the alphabet or numbers. The later results of these methods are exceptional and far above averages because they've learned ways to DO things before learning abstracts.

So teach tables, tricks and whatever so we can get the answers we need then explain the proof of each one. Those blessed with maths talents will be interested to know more and capable of pursuing the subject to an academic level. Surely, the college student faltering at sticky problems that his 'tricks' don't cover is simply one who does not have a mathematical mind.

We don't demand that every driver can build their own car and maths USERS outnumber mathematicians by a factor of, erm, what - a whole bunch, right? ;)

re: 10 Easy Math Tricks You Probably Don't Know

Scotty/Sioux City — Sun, 17 Feb 2008 17:55:43 GMT

Why are there only 5 "tricks" when the title of the article suggests that you were going to show us 10 tricks??? Am I the only person reading this that can count??? Does that count as one of the tricks??? Scotty

re: 10 Easy Math Tricks You Probably Don't Know

alm260 — Sat, 16 Feb 2008 23:26:10 GMT

I hate math and I just love the quote from the movie "Peggy Sue Got Married" starring Kathleen Turner (she ends up time traveling to her past in high school)...

[Peggy Sue hands in her algebra test]

Mr. Snelgrove: And what's the meaning of this, Peggy Sue?

Peggy Sue: Well, Mr Snelgrove, I happen to know that in the future I will not have the slightest use for algebra, and I speak from experience.

I agree!

re: 10 Easy Math Tricks You Probably Don't Know

dtariq — Sat, 16 Feb 2008 22:44:37 GMT

meow

re: 10 Easy Math Tricks You Probably Don't Know

Yeshuas Girl — Sat, 16 Feb 2008 15:06:14 GMT

Thats really COOL!!! I'm going to start using that for my Math!!!!! Thanks aftertherayn!!!

re: 10 Easy Math Tricks You Probably Don't Know

s-orion — Sat, 16 Feb 2008 14:30:24 GMT

There are many ivory towers for mathematicians, but applied mathematicians have a basic need to serve others, by helping solve real world problems. They are condemned to wander the world, masquerading as engineers. There are few, but that is good, because few are needed. They carry calculus, differential equations, matrices, and linear transformations like tools in their bag. They may share the explanation of tricks, but never pull them on others, because they know, it is the height of arrogance and abuse of talent to laud over and not serve others, less understanding than they.

Please do not be too hard on the ivory tower mathematicians; many of their flights of fancy-castles in the air have found practical application. There need to be both kinds.

A trick for you all that has practical application; when the balance in your checkbook doesn’t square with the bank’s number, it is a good common thing to look for the exact difference somewhere in your check register or on the bank sheet. That’s OK, and if you find it, that’s great.

But if not, before doing more, divide that difference, by nine. If it divides evenly, there is a good chance you have transposed two adjacent numbers somewhere; an easy error to, exasperatingly, overlook. No guarantees, just a possible clue to minimize the tearing out of hair!

Good Luck and Steady Winds

re: 10 Easy Math Tricks You Probably Don't Know

s-orion — Sat, 16 Feb 2008 14:28:32 GMT

Whitebuffalobk and and Sonnie Moonie are so right. When in a small college, I took all the math courses I could, from the engineering arm, not the sciences arm of the school, thus, unwittingly, creating an applied mathematics major for myself, where there was no formal one.

Had to go to the big university at the capitol to take my Graduate Record Examination (GRE). Consisted of a general part and then a second part in one’s major. Before each part, multiple choice answer sheets were handed out, that were to be marked. All students, (about 400 in the auditorium), got an idea of the difficulty of the questions to come, by the number of answers to be marked on the sheets. They were abuzz as the history and English majors had 300 +, the chemistry and physics majors nearly 200. Finally, the call came for math majors to come down and get their sheet. Only one other person got up and came down with me to each get our sheet. We gasped, as there were only 80 or so answer places.

I carefully noted where he sat back down way over on the other side and in front of me in the auditorium. I did my best, but when I got to the last five questions, I had never seen them before. However, I had been well grounded in applying the principles and slowly worked my way through them all, getting done with a modest time left before the buzzer. The other student worked right up to the end, before he turned in the question pamphlet and answer sheet.

I eagerly waited for him to come out to the foyer to talk about the test. Turns out, he was from the big University. To my surprise, he said he was pretty sure he had seen the tricks to most of those last ten tough questions, but couldn’t remember the tricks exactly. He struggled to guess as best he could, but ran out of time and didn’t even get to mark anything down on some of them.

It was the first of many clues I was to get in life, about tricks versus basics and applied mathematicians versus mathematicians.

(help in next email)

re: 10 Easy Math Tricks You Probably Don't Know

mirjensil — Sat, 16 Feb 2008 14:25:56 GMT

The title of the article is "TEN EASY MATH TRICKS YOU PROBABLY DON'T KNOW."

What happened to numbers 6-10? I only see 5 listed.

Also, there's another article entitled "How to Achieve Deep, Uninterrupted Sleep

Use these 24 simple tricks to help you get the sleep you need."

Yet only 10 are listed.

Am I missing something or is math really trickier than I previously thought? :)

re: 10 Easy Math Tricks You Probably Don't Know

jmat33r — Sat, 16 Feb 2008 12:48:57 GMT

What so you think of the NEW MATH being taught in various school around the nation these days?

re: 10 Easy Math Tricks You Probably Don't Know

amadeus49 — Sat, 16 Feb 2008 11:41:31 GMT

". . . take the first numerial of that number, 2, and place it to the right side of the answer, then take the second numerial, 3, and place it to the left side of the answer, now add the two numerals together 2 + 3, which equals 5 and place it in the middle of the answer.....2 5 3. If the number is 29 X11, you still put the 2 to the left, the 9 to the right, add 2 + 9 which equals 11, so put the 1 in the middle and then add 2+1 . . . "

Right ! Heaven help anyone who relies on this or similar approaches to basic math.

I would have a much harder time remembering most of these "tricks". If I had to memorize something, I'd stick with the basic concepts that the math teacher whitebuffalobk talks about.

I was fortunate to have a similar inspirational math teacher who introduced me to both, but the basics came first, then the fun and tricks later on as proofs or mental exercises.

re: 10 Easy Math Tricks You Probably Don't Know

whitebuffalobk — Sat, 16 Feb 2008 07:24:33 GMT

As a math teacher myself...both high school and college level...are you going to try to memorize a trick to do every type of arithmetic problem? Why not just learn how to do the problems correctly to start with. Tricks and jingles which work with just a few problems may be "fun" but they do not create concept skills that build upon one another in high school math. And when these students get into one of the upper-level math classes which expect this background to be in place, not only do they have an answer as to why a "trick" works, they often resent the teacher who is trying to get them to really learn a concept. Math consists of more than just arithmetic and tricks. It's an exciting, beautiful subject in its own accord. Please treat it with the respect it deserves and stop trying to side-track students who could actually learn the subject matter with tricks. Maybe then the failure level in freshman college level classes will finally go down.

re: 10 Easy Math Tricks You Probably Don't Know

hunter3738 — Sat, 16 Feb 2008 06:46:23 GMT

Did you know why 37 is a magic number ? Here's why. If you divide any number consisting of 3 identical digits by the sum of these digits, the result is always 37 eg 666 / (6+6+6) = 555 / (5+5+5) = 37 etc.

Proof: (100.x + 10.x + x) / (x+x+x) = (100 + 10 + 1).x / (1+1+1).x = 111.x / 3.x = 111 / 3 = 37

re: 10 Easy Math Tricks You Probably Don't Know

LDCR — Sat, 16 Feb 2008 05:17:44 GMT

I actually knew the first example in a different form and almost didn't recognise it.

If you want to square a number ending in .5, then you multiply the closest whole numbers either side of it together and add .25

e.g:

6.5 squared is 6 x 7 + 0.25 = 42.25

re: 10 Easy Math Tricks You Probably Don't Know

aftertherayne — Sat, 16 Feb 2008 04:33:45 GMT

You can directly write down the answer to any number multiplied by 11.

* Take for example the number 51236 X 11.

* First, write down the number with a zero in front of it.

051236

The zero is necessary so that the rules are simpler.

* Draw a line under the number.

* Bear with me on this one. It is simple if you work through it slowly. To do this, all you have to do this is "Add the neighbor". Look at the 6 in the "units" position of the number. Since there is no number to the right of it, you can't add to its "neighbor" so just write down 6 below the 6 in the units col.

* For the "tens" place, add the 3 to the its "neighbor" (the 6). Write the answer: 9 below the 3.

* For the "hundreds" place, add the 2 to the its "neighbor" (the 3). Write the answer: 5 below the 2.

* For the "thousands" place, add the 1 to the its "neighbor" (the 2). Write the answer: 3 below the 1.

* For the "ten-thousands" place, add the 5 to the its "neighbor" (the 1). Write the answer: 6 below the 5.

* For the "hundred-thousands" place, add the 0 to the its "neighbor" (the 5). Write the answer: 5 below the 0.

That's it ... 11 X 051236 = 563596