Easy Math Tricks that can be done in your Head to Impress Friends and Family

Wayne Ramsey's image for:
"Easy Math Tricks that can be done in your Head to Impress Friends and Family"
Image by: 

Math tricks can be a fun way to impress friends and family alike.  Someone that has the knowledge of how to perform quick math tricks can make a simple math class a lot more entertaining while also making the solving a problems much easier than it would normally be.  There are numerous math tricks out there for a wide variety of problems.  Learning how to do the tricks quickly will make them that much more impressive.  It takes a little bit of practice to get a quick routine down but once it is mastered it can make anyone appear to be a math genius.

Figuring out the Square Root

For numbers that are 2 digits ending with a 5, figuring out the square root can be done really easily with some very simple math.  By taking the very first number and adding a one to it then multiplying it by itself the first number is created.  Then simply add 25 to the end of that number.  To make it a little more understable here is an example

The square root of 35 would look like this:  3 (first number) +1= 4, then multiply the 4 times the original number of 3.  This leaves 12.  Then you simply add 25 to the end of it for an end result of 1225, which is the square root of 35. 

Multiplying Large Numbers by 5

Multiplying by 5 is pretty easy until it gets into the larger numbers.  At this point in time it becomes a lot more complicated as a little more memory power is needed.  To do multiplications by 5 easier it is all about knowing the simple tricks. 

I will use 1350 as an example.  To find out what this is multiplied by 5, I simply take 1350 and divide it by 2.  This results in 675.  Since the division resulted in a whole number I then simply add a 0 to the end of it to make 6750.  If the number isn't a whole number it becomes only slightly more difficult.  Instead of adding a zero to the end of it, I remove the numbers behind the decimal point after the division and instead of adding a 0 I would add a 5 instead.  So for example 1353 divided by 2 would be 676.5.  I would remove everything behind the decimal to get 676 and would then at a 5 to the end of it to get 6765. 

Making tough Multiplication Easier

Multiplication isn't all that difficult but some of the more complicated multiple problems can be made considerably easier if the logic behind them is better understood.  Just like with fractions, multiplication can be done by reducing the multipliers down to the lowest possible number making it easier to do the math in your head.  To do this, simply find a number that you are comfortable dividing the first number by.  If the number is 16, then divide it by 4 to create 4.  Then multiply the second number by the same amount that the first number was divided by.  Assuming this number was 52, then you now have 208.  4 x 208 which can be reduced further to 2 x 416.  This math is much easier than doing the original problem of 16 x 52.  It has the same result but much easier to accomplish. 

Here is how the example would look so that it is a little bit easier to understand.  start with 16 x 52.  By dividing the first number by a number that it is easily divisible by such as 4, I get 4.  I then use that same number on the second number but rather than dividing I must multiply.  This gives me 208.  I now have 4 x 208.  This is an easy math problem that would equal 832.  However, I can make it even easier by reducing it again by dividing by 2 to get 2 and multiplying the second half to get 416.  I now have 2 x 416 or the same 832 that I got previously. 

By using this method it is possible to do math in the head that would have been much more complicated if the original 16 x 52 were used. 

Dividing by 5

Dividing by 5 can be just as easy as multiplying larger numbers by 5.  When it comes to the division it is simply a matter of moving the decimal point and there are even fewer rules involved in division than there are in the multiplication of 5s.  Simply take the number that is being divided by 5 and multiply it by 2. 

For example, if I want to divide 177 by 2, then I would start by multiplying 177 x 2.  This comes out to 354.  Now that I have this number I simiply move the decimal point forward.  354 would then become 35.4 and the answer to the problem.  This method can be done with any size problem but obviously becomes more difficult to do in your head the bigger the number becomes. 

More about this author: Wayne Ramsey

From Around the Web