# Cool math tricks

This unit is dedicated to showing you a variety of cool math tricks that can help you tackle some basic math problems with speed and great accuracy. We start with a math trick that you can use to square a number easily and fast.

Take a close look at the figure below! It shows how you can use a cool math trick to square a two-digit number much faster than the traditional way of doing it.

The goal is to rewrite one of the numbers being multiplied so that it will have 1 or more zeros. At this point, there may be one thing that you may not quite understand. Why did we add 42 to 10 × 18 ? Keep reading as we show you the math behind it!

10 × 18 = (14 - 4)(14 + 4)

10 × 18 = 14 × 14 + 14 × 4 - 14 × 4 - 42

10 × 18 = 14 × 14 + 56 - 56 - 42

10 × 18 = 14 × 14 - 42

Now, all we have to do is to add 42 to both sides of 10 × 18 = 14 × 14 - 42

10 × 18 + 42 = 14 × 14 - 42 + 42

10 × 18 + 42 = 14 × 14 (Here we go!)

In general,

Let X and c be a natural number. If X + c or X - c gives a number that has 1 or more zeros, then you can multiply X by X easily using the equation  X2 = (X + c)(X - c) + c2

## Here are a few more interesting and cool math tricks!

Multiplying by powers of ten
Learn to multiply by powers of ten the easy way with these useful shortcuts tricks

Multiplication by 11
Learn how to perform multiplication by 11 in 10 seconds or less with these useful tricks

Squaring numbers ending with five
What if you could square any number two digit number ending in five in 4 seconds or less?

Finger multiplication
Easy, straightforward, and quick multiplication with your fingers!

Number trick with 1089
impress your friends with this 1089 trick!

Compensation
Learn how to use compensation to quickly add, subtract, divide, and multiply

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