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Multiplying two numbers between 10 and 20

16 × 12

Multiplication of those numbers whose Difference is 10 and last digits are 5:

STEP 1: Square of the first digit of the greater number
STEP 2: Substract 1 from Square
STEP 3: Add 75 in last

Multiplication of two ADJACENT NUMBERS

Follow the following Steps:
Step1: Square the First number
Step 2: Add that number in Square

Squaring a 2-digit number which is between 25-50

Find the Square of 43
Step-1: find the difference(d) with 50==>43 is 7 less than 50 so d=7
Step-2:find the square of difference(d)  ==> Square of 7 is 49,so it is our 1st part.
Step-3: Now find difference of  25 and 'd' ==>25-7=18, it is second part.
              So our answer is 1849

SQUARING A 2-DIGIT NUMBER WHICH ENDS IN 5

TRICKS
STEP 1:Last two digits of the square are always 25.
STEP 2: To find the number which comes before 25, just perform the operation a x (a+1),where a   
                is the digit before 5 in the original number.
STEP 3. By putting the number received in step 2, just before 25 and you get your square.


Example: Find the square of 75?
                  If we want to square 75, we can find the same in the following steps –
STEP 1:1. Last two digits are 25.
STEP 2. The digit before 5 is 7, if we perform a x (a+1) operation on this,then we will be 
                 7 x (7+1) = 56
STEP3. Hence the square of 75, will be 5625.

Multiplying two 2-digit numbers (same 1st digit, 2nd digits sum to 10)

Step 1:Choose second digits whose sum is 10.
Step 2:Multiply the first digit by one number greater than itself; this number will be the first part of the answer:
X X _ _.
Step 3:Multiply the two second digits together; the product will be the last part of the answer: _ _ X X.
Note: If the two second digits are 1 and 9 (or, more generally, have a product that is less than ten), insert a 0 (zero) for the first X in step 4.

Squaring a 2-digit number beginning with 5

Step 1:Take a 2-digit number beginning with 5.
Step 2: Square the first digit.
Step 3: Add this number to the second number to find the first part of the answer.
Step 4:Square the second digit: this is the last part of the answer.