# Tagged with maths

# Maths Trick ==> How to Multiply Double-Digit Numbers by 11

## How to Multiply Double-Digit Numbers by 11

All you need to do is add the digits of the number you are multiplying by 11 and place that in the middle of the original number. If the sum of the digits is 10 or larger, simply carry it over. Better to see it than me write it.

See how easy that was? Basically, if you know how to add, you know how to multiple by 11.

Now, let’s look at another example.

**11 x 11**

Just separate the number being multiplied by **11** (in this case, also **11**) so that there’s room for your number in-between. Now, just add the two digits in that number together (**1 + 1 = 2**) and throw the sum in that space you left open. That gives you **121**.

**58 x 11**

Just add **5 + 8**, which gives you **13**. The slide it in-between the **5** and **8** and you get **5138**. But, that’s not right, since you need to carry that one over. Go ahead and carry it over and you’ll end up with **638**.

Needless to say, I feel like a complete badass now that I know this.

# Maths Tricks ==> MULTIPLICATION OF 2 TWO-DIGIT NUMBERS

**MULTIPLICATION OF 2 TWO-DIGIT NUMBERS WHERE THE FIRST DIGIT OF BOTH THE NUMBERS ARE SAME AND THE LAST DIGIT OF THE TWO NUMBERS SUM TO 10**

###### Let me explain this rule by taking examples

###### To calculate 56×54:

###### Multiply 5 by 5+1. So, 5*6 = 30. Write down 30.

Multiply together the last digits: 6*4 = 24. Write down 24.

###### The product of 56 and 54 is thus 3024.

EXAMPLE.

Understand the rule by 1 more example

78*72 = [7*(7+1)][8*2] = 5616

# Maths Tricks ==> SQUARE OF ANY 2 DIGIT NUMBER

**SQUARE OF ANY 2 DIGIT NUMBER**

#####
Let me explain this trick by taking examples

67^2 = [6^2][7^2]+20*6*7 = 3649+840 = 4489

##### similarly

25^2 = [2^2][5^2]+20*2*5 = 425+200 = 625

##### Take one more example

97^2 = [9^2][7^2]+20*9*7 = 8149+1260 = 9409

Here [] is not an operation, it is only a separation between initial 2 and last 2 digits

##### EXAMPLE.

Here an extra case arises

Consider the following examples for that

91^2 = [9^2][1^2]+20*9*1 = 8101+180 = 8281

# Maths Trick ==> SQUARE OF NUMBERS NEAR TO 100

**SQUARE OF NUMBERS NEAR TO 100**