Introduction
In mathematics tricks are important to do
calculation faster and easier. In these slides
we will show you some tricks for fast and
easy calculation.

Multiplying by 4
This trick is very simple and yet logical. To multiply any
number by 4, just multiply it by 2 and then double the
answer. The basic concept of this trick is that you can
solve a multiplication problem by multiplying by its
factors. Let’s assume the number is 25.
Then:
25 x 4
25 x 2 = 50
50 x 2 = 100
25 x 4 = 100
This trick is based on a very simple fact:
2 x 2 = 4

Multiplication by 5
It's often more convenient instead of
multiplying by 5 to multiply first by 10 and
then divide by 2.
For example, 137×5 = 1370/2 = 685.

Multiplying by 12
12 X 7
The first thing is to always multiply the 1 of the twelve by
the
number we are multiplying by, in this case 7. So 1 X 7 =
7.
Multiply this 7 by 10 giving 70. (Why? We are working
with BASES here.)
Bases are the fundamentals to easy calculations for all
multiplication tables.
Now multiply the 7 by the 2 of twelve giving 14. Add this
to 70 giving 84.
Therefore 7 X 12 = 84

Multiplication of 2 Numbers
Step 1:
Let us consider multiplying any two digit numbers, for example 23 x 24.
Step 2:
Choose the unit digit of both the numerals and deduct it from the given numerals.
23 - 3 = 20
24 - 4 = 20
Step 3:
Now, select any one number (24) and add it with unit digit of another number(3)
24 + 3 = 27
Step 4:
Then, multiply the result obtained in step 2 and step 3.
27 x 20 = 540
Step 5:
Multiply the unit digit values.
4 x 3 = 12
Step 6:
Finally, add values obtained from step 3 and step 4.
540 + 12 = 552
23 x 24 = 552

Multiplication of 3 Numbers
Step 1:
Let us consider multiplication of three digit numbers 208 x 206.
Step 2:
Now, deduct the last digit from the respective numerals.
208 - 8 = 200
206 - 6 = 200
Step 3:
Pick any one number and add it with the unit digit of another number.
208 + 6 = 214
Step 4:
Now, multiply the result obtained in step 1 and step 2.
214 * 200 = 42800
Step 5:
Then, multiply the unit digits of the given numbers.
8 * 6 = 48
Step 6:
Add the values obtained in step 4 and step 5.
42800 + 48 = 42848
208 x 206 = 42848

To check divisibility of a number
2- A number is divisible by 2 if it is even.
3- A number is divisible by 3 if the sum of the digits is a multiple of 3.
Eg.)12-1+2=3
4-A number is divisible to 4 if the last two digits of the number are
divisible by 4.
5-A number is divisible by 5 if the last digit is 5 or 0.
6-A number is divisible by 6 if the number is divisible by 2 and 3.
7-A number is divisible by 7 if you double the last digit and subtract it
from the rest of the number and the answer is: 0, or
divisible by 7.
8-The last three digits are divisible by 8.
9-The sum of the digits is divisible by 9.
10-The number ends in 0.
11-If you sum every second digit and then subtract all other digits and the
answer is:0, or divisible by 11.
12-The number is divisible by both 3 and 4.

Squaring of numbers ending with 5
65x65=4225
Multiply the previous number 6 to one more
than itself 7. Then write 25.

Squaring two digit numbers
Say, you want a square of 13. Do this: add 3
(the last digit) to 13 (the number to be
squared) to get 16 = 13 + 3. Square the last
digit: 3² = 9. Append the result to the sum:
169.

Distributive Property
The Distributive Property is an algebra
property which is used to multiply a single
term and two or more terms inside a set of
parentheses.
Eg.) 103+101=100(3+1)