Math beats

How to divide a large number by 5 in seconds?
Step 1:Multiply the number by 2. Step 2:Move the decimal point in the product one place to the left.

EXAMPLE: 195 / 5, Step 1:195 x 2 = 390.0 Step 2: Move the decimal one place to the left: 39.0 Try 392978 / 5!

Everyone can multiply by a two digit number by 11 but how quickly...

Step 1:Consider the original number and imagine a space between two digits. Step 2:Then, add the two digits and put the sum in the space.

EXAMPLE:52 x 11, Step 1:Write 52 as 5_2. Step 2: Then, 5(5+2)2=572. Try 49 x 11!

Squaring a number ending in 5 in a blink of eye...

Step 1:Multiply the successor of ten's digit of the number with ten's digit. Step 2:Square 5 to get 25.

EXAMPLE:Square of 25 Step 1:Multiply ten's digit 2 with its successor 3, 2 x 3 = 6 Step 2:Square of 5 = 25 So, square of 25 = 625 Try square of 55!

Square root of a perfect square

Example: √5184 Step 1:Pair the numbers from right to left 5184. We get two pairs. Therefore, the answer is a 2 digit number. Step 2:Find a number whose square is the nearest to second pair 51. Square of 7 = 49 and square of 8 = 64. 49 is less than 51 . Therefore first digit of square root is 7. Step 3:Look at last digit which is 4 of the number 5184 . As square of 2 = 4 and square of 8 = 64 both end with 4 , the answer could be 72 or 78 . Step 4:As we know square of 75 = 5625 greater than 5184 , √5184is below 75 . So, √5184 =72

Multiplication of a Three digit numbers

175 x 157 = ? The result of multiplication of three digit number is 175 x 157 = 27475. Step 1: Multiply (5 x 7) = 35 (note down 5 carry 3) Step 2:Then do cross multiplication (7 x 7 + 5 x 5 + 3 (add carry)) = 77 (note down 7 carry 7). Step 3: Again (1 x 7 + 1 x 5 + 7 x 5 + 7 (add carry)) = 54 (note down 4 carry 5). Step 4:do cross multiplication and add carry (1 x 5 + 1 x 7 + 5 (add carry)) = 17 (note down 7 carry 1). Step 5: Again (1 x 1 + 1) = 2, note it down. And finally the result we get 27475

Try this: Take 15 x 13 for an example. Always place the larger number of the two on top in your mind. Then draw the shape of Africa mentally so it covers the 15 and the 3 from the 13 below. Those covered numbers are all you need. First add 15 + 3 = 18 Add a zero behind it (multiply by 10) to get 180. Multiply the covered lower 3 x the single digit above it the "5" (3x5= 15) Add 180 + 15 = 195.

EXCEPTIONAL DIVISION RULE FOR 4
If a number is divisible by four the last two digit are divisible by 4 (or are zeros). EXAMPLE. 45624 last two digit is 24 24 is divisible by 4 then 45624 is divisible by 4.

GOLDEN DIVISION RULE FOR 3
If a number is divisible by three, the sum of its digits will be divisible by 3. EXAMPLE 372 = 3 + 7 + 2 = 12 A corollary of this is that, any number made by rearranging the digits of a number divisible by 3 will also be divisible by 3.

Multiplication of any two numbers, lies between 11 and 19
Add first number and last digit of the second number take zero in the third place of this number then add product of last digit of the two numbers in it. Let me explain this rule by taking examples 13*19 = ? = (13+9)*10 + (3*9) = 220 + 27 = 247

Squaring Technique to speed up calculations
In case of two digit number deduct last digit and add it to another number and then add square of same. Example: (53*53)=? = (53+3) * (53-3) +