In this blog, I'm going to talk about why maths tricks never appeal to me. The first trick, I learned was introduced by high school teacher on how to compute squares of number ending with digit 5.
Here is how it works
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Step1: Take any number ending with 5, lets say 65
Step2: Place the square of 5 in last two digits of the result.
Step3: Add 1 to 6 =7 and multiply it by 6; that is 7x6 = 42
Step4: Answer = 42 25
Here is pictorial representation of the technique
Isn't simple and fascinating? Well ya! Compare how much time you would have taken without this trick. This definitely saves my time while calculating small numbers up to 4 digit may be. But after four digits, I am better off computing with regular method of squaring numbers.Here, is an another example
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Let's divide the number 221013 by 9?
In this case, what they call trick is simple, Write the most significant digit as it is, which is followed by diagonal addition with the number itself. Let's try with an example.
I'm sure you can save time in calculation if following holds true1. You were asked to divide by 9
2. You remember this method
3. You recollect the methods on seeing such problem.
Well, that's too many conditions to hold true at same time. My more bigger concern, how about division by 7, 8 ? There may be some tricks for them too but there is nothing like each trick for every operation. Even if there are, you are not going to remember, so why bother.
Now put your self in situation, where you just learned few maths tricks, and you given a simple problem divide 24556 by 8. You must be scratching your head, tinkering about various tricks you learned. If none exist or you forgot some steps, you already lost most of the time you would have gain with the trick. Worst, you might not feel very confident with the answer. As most people understand the steps but not sure how these techniques work or do they work always :). And now what! you ended up verifying your answer with regular approach and finally realizing oh shoot!, What am I doing?
In nutshell, what I really want to say, the maths tricks are like fantasies which we want to learn but may not practically be able to use them. There would be numerous maths tricks exists today, even though if we master most of them, recollection, verification, incompleteness are going to cost more. Thus, you are better off following the arithmetic fundamentals.
I personally prefers methods which are based are follow up of fundamentals like
Compute Square of 98 = square(100 - 2) = 10000 - 200 + 4 as additions are easier than multiplications. Anyway, if you happen to be scratching your head to compute the fastest then just follow the basics.
P.S. comments are welcome! :)
