Divisibility Rules

Dividing by 3 Add up the digits: if the sum is divisible by three, then the number is as well. Examples: 111111: the digits add to 6 so the whole number is divisible by three. 87687687. The digits add up to 57, and 5 plus seven is 12, so the original number is divisible...

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Short-cut to find square of any number

Eg 1) 362    Step 1: Choose the base number.36 is closer to 40. Therefore 40 is the base number. Step 2:Find how much the given number is more or less of the base number.36 is  -4 of 40. Step 3: Square the difference. (-4)² =16. Step 4: Add the difference to...

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A Mind-Blowing 3-Digit Number Squaring Shortcut

Now You Can Square Any Number Whose Tens Digit is 5 Without Using a Calculator To begin with, I shall first introduce my canny friend, the Rules. It will be necessary to examine these rules in order to make your way about this method simpler. Since the tens digit has already...

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Multiply Up to 20X20 In Your Head

In just FIVE minutes you should learn to quickly multiply up to 20x20 in your head.  With this trick, you will be able to multiply any two numbers from 11 to 19 in your head quickly, without the use of a calculator. I will assume that you know your...

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Divisibility by prime numbers under 50

A number is divisible by 2 if its last digit is also (i.e. 0,2,4,6 or 8). A number is divisible by 3 if the sum of its digits is also. Example: 534: 5+3+4=12 and 1+2=3 so 534 is divisible by 3. A number is divisible by 5 if the last digit is 5 or 0. Most people...

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Squaring numbers ending in 1

Here’s a simple trick to square any number that ends in 1. Subtract 1 from the number. Square the difference. (Squaring of such number is easy as it ends in ‘0’) Add the difference twice to its square. Add 1. Example: If the number to be squared is...

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Divisibility Rules

Dividing by 3 Add up the digits: if the sum is divisible by three, then the number is as well. Examples: 111111: the digits add to 6 so the whole number is divisible by three. 87687687. The digits add up to 57, and 5 plus seven is 12, so the original number is divisible...

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Number Notations for Maths

Hierarchy of Decimal Numbers Number Name How many 0 zero 1 one 2 two 3 ...

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Subtraction Tricks

An operation of finding an addend by a sum and another addend: 17 – 6 = 11.  Here 17 is a minuend,  6 – a subtrahend,  11 – the difference. Math tricks 1: subtracting by oversubtracting 251-85 =(151+100)-85 =151+100-85 =151+15 =166 In this example,251...

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Addition Tricks

Addition -an operation of finding a sum of some numbers: 21 + 5 = 26. Here 21 and 5 – addends,  26 – the sum. If addends are changed by places, a sum is saved the same: 21 + 5 = 26 and 5 + 21 = 26. Math tricks 1: Adding by breaking apart a number Example: 137+85 =(122+15)+85 =122+100 =222 In...

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History of Maths

An overview Mathematics starts with counting. It is not reasonable, however, to suggest that early counting was mathematics. Only when some record of the counting was kept and, therefore, some representation of numbers occurred can mathematics be said to have started. In...

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Division Tricks

An operation of finding one of factors by a product and another factor: 48÷4 = 12. Here  48  is a dividend,  4 – a divisor,  12 – the quotient. At dividing integers a quotient can be not a whole number. Then this quotient can be present as a fraction....

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IMPRESS YOUR FRIENDS WITH MENTAL MATH TRICKS

Easy Cal Tricks Being able to perform arithmetic quickly and mentally can greatly boost your self-esteem, especially if you don't consider yourself to be very good at Math. And, getting comfortable with arithmetic might just motivate you to dive deeper into other things...

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