Magic Math Tricks for Fast Mental Calculation

Math is a trouble and tension for some people especially for some students having math phobia. Here are some of the math tricks that help in easy calculation. And there will be no need of pen, pencil and paper as it will allow you to calculate in your head. And leads to increase your mental abilities of calculations and also reduces the fear of math. 

Multiplying a number with 11:

If you want to multiply a number say 45 with 11. This can be possible only in simple 3 steps:
Write 45 as 4 [  ] 5 where [  ] is a space for a new digit that will be filled in the middle
Find the middle digit as 4 [4+5] 5. The middle digit is the sum or total of 2 digits.
The number is 495.

And if the sum of 2 digits is more than 9 i.e. a 2 digit number. If the number is 69 to multiplied with 11
Write 69 as 6 [  ] 9
Find the middle digit as 6[6+9]9 = 6 [15] 9. Since the middle digit is not actually a digit but a 2 digit number, so add 10 to first digit and retain 4 in the middle.
The number is 6+1 (5) 9 = 759.

Square of a number that ends in 5:

Try finding the square of 75 in your head.
Take the digit in the tens place i.e. 7 and multiply it with its successor i.e. 7+1 = 8. The result is 56
Now put 25 at the end of the result i.e. 5625.  So 5625 is the square of 75. That is your answer.
This math trick can be used anytime you have to find square of a number ending in 5. It applies to 3 digit numbers also.
So the square of 115 is:
First multiply 11 with its successor i.e. 12 = 132.
Now add 25 at the end. Your answer is 13225.

Divide a number by 5:

If you want to divide any number by 5.  For example if you want to divide 925 by 5. It can be easily possible using following trick:
Double the number i.e. multiplies it by 2. So you get 1850
Now move decimal point one step to the left i.e. reduce one 0. So the answer is 118.
This trick also can be applied to decimal numbers. Let us use it with 382.3
Double up the number. So you get 764.6
Now move the decimal point to the left by 1 position. So you get 76.46.

Multiplying a number with 5:

To multiply any number with 5 is equal as multiplying it with 10 and dividing it by 2. If you want to multiply 456 with 5.
Divide the number by 2 i.e. 228
Now add 0 at the end. The answer is 2280
If the answer is in decimal the same rule will apply. To multiply 1155 with 5:
Divide the number by 2 i.e. 577.5
Now multiply it by 10 i.e. 5775. This is same as adding a 0 at the end or moving a decimal point one step to the right.

Multiplying a number with 9:

If you want to multiply a number by 9, this trick will help if you are fast with subtraction. If you want to multiply 73 with 9.
At 0 at the end of the number i.e. 730
Subtract original number from the new number i.e. 730 - 73 = 657

Thus by practicing these tricks daily you can easily get the answer and also will results in fast calculations. Also comment below if these math tricks help you in easy and fast mental calculation. And also suggest other math tricks if you know any.