Let me precede this by saying that I'm sure that billions of people have already realized this, and I'm probably late to the game by not doing so. I'm only posting this for the 12 people that never realized that you could do this.

Everybody knows the following:

`(x+y)(x-y) = x^2 - y^2`

Now, this fact makes a simple "trick" possible. If you have 2 numbers equidistant from a value whose square you know, you can easily multiply them together.

Say you want to multiply 24 and 26. Set 25 as X, and recall that 25^2 = 625. Since you chose 25 for X, Y is 1. The final answer is 624. That's something that you can do in your head. It works for everything, and it makes it a little easier to have instant answers for more math inquiries.

Let's stress again that this isn't just for values 2 apart. 62*78 would have an X of 70 and a Y of 8, so you'd have 4900-64=4836 as an answer, something that isn't obviously prone (to an observer) to any trick at all. Similarly, 109*113 would be 12321-4=12317.

## 5 comments:

Unlike other conjectures you may have posited in the past, this one is mathematically sound. Congrats!

Reminds me of a neat video of Professor Benjamin from Harvey Mudd:

http://www.ted.com/index.php/talks/view/id/199

I haven’t any word to appreciate this post.....Really i am impressed from this post....Looking for the high-quality Granite countertops then, legacymarbleandgranite.com is the best option for you. Visit us on granite countertops lima

This is very educational content and written well for a change. It's nice to see that some people still understand how to write a quality post.! Best sand proof beach towel service provider.

It’s actually a great and helpful piece of info. I’m happy that you just shared this helpful info with us. Please keep us informed like this. Thanks for sharing! Best internship for fashion stylist service provider.

Post a Comment