10 Great Math Tricks to Do Calculations in Your Head

Wed, 19 Sep 2007 02:53:25 GMT

clipped by: constantskeptic
clipper's remarks: this is a great detailed list of helpful math tricks, most of them I didn't know before.

Clip Source: listverse.com

10 Easy Arithmetic Tricks

Clip Source: listverse.com

1. The 11 Times Trick

We all know the trick when multiplying by ten - add 0 to the end of the number, but did you know there is an equally easy trick for multiplying a two digit number by 11? This is it:

Take the original number and imagine a space between the two digits (in this example we will use 52:

5_2

Now add the two numbers together and put them in the middle:

5_(5+2)_2

That is it - you have the answer: 572.

If the numbers in the middle add up to a 2 digit number, just insert the second number and add 1 to the first:

9_(9+9)_9

(9+1)_8_9

10_8_9

1089 - It works every time.

2. Quick Square

If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!

25² = (2x(2+1)) & 25

2 x 3 = 6

625

3. Multiply by 5

Most people memorize the 5 times tables very easily, but when you get in to larger numbers it gets more complex - or does it? This trick is super easy.

Tags: math, arithmetic, tricks, lists, useful, tips

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10 Great Math Tricks to Do Calculations in Your Head