I don't know if this should be in the book section (if there is any) or here...

Here is what I came across this book in a site called StudentsDiary.

Secrets of Mental Math
The Mathemagician’s Guide to Lightning Calculation and Amazing Math Tricks
By Arthur Benjamin and Michael Shermer.

INSTANT MULTIPLICATION
Let’s begin with one of my favorite feats of mental math—how to multiply, in your head, any two-digit number by
eleven. It’s very easy once you know the secret. Consider the problem:
32 × 11
To solve this problem, simply add the
digits, 3 + 2 = 5, put the 5 between the 3 and the 2, and there is your answer:
352.

Get the full and free e-book Here

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1st to comment.....dancing skeleku