Today we are sharing some special cases of multiplication which will help you to solve simplification problems quickly and easily. Try to apply these techniques for speedy calculations and keep practicing !!
I have already shared Vedic maths trick to Multiply large numbers here.
GENERAL RULES FOR MULTIPLICATION
Step 1 - Multiply the right hand side digits
Step 2 - Cross-Multiplication
Step 3 - Multiply the left hand side digits
ANSWER = 4402
MULTIPLICATION BY A 3-DIGIT NUMBER
EXAMPLE - 198 × 256
Step 1 -
Step 2-
Step 3 -
Step 4 -
Step 5 -
MULTIPLICATION BY A 4-DIGIT NUMBER
EXAMPLE - 4325 × 3216
Step 1 -
Step 2 -
Step 3 -
Step 4
Step 5
Step 6
Step 7
Multiply by 5
To multiply any number with 5, we will
"MULTIPLY THE NUMBER WITH 10 AND DIVIDE IT WITH 2 "
EXAMPLE
Multiply 2469 by 5
Step 1 - Multiply 2469 with 10
=> 2469 × 10 = 24690
Step 2 - Divide 24690 by 2
=> 24690/2 = 12345
ANSWER = 12345
MULTIPLY BY 9
To multiply any number with 9, we will
" MULTIPLY THE NUMBER WITH 10 AND SUBTRACT THE NUMBER ITSELF "
EXAMPLE
Multiply 4582 by 9
Step 1 - Multiply 4582 with 10
=> 4582 × 10 = 45820
Step 2 -Subtract the number itself from the result
=> 45820 - 4582 = 41238
ANSWER = 41238
MULTIPLY BY 11
To multiply any number with 11,we will
" WRITE ZERO TO THE LEFT SIDE OF THE NUMBER. KEEP THE LAST DIGIT SAME AND START ADDING THE SUCCESSIVE DIGITS FROM RIGHT HAND SIDE "
OR
" MULTIPLY THE NUMBER WITH 10 AND ADD THE NUMBER ITSELF "
EXAMPLE
Multiply 89067 by 11
Step 1 - Write zero to the left side of the number.
=> 089067
Step 2 - Keep the last digit same and start adding the digits from right hand side.
=> 
ANSWER - 979737
OR
Step 1 - Multiply the number with 10
=> 89067 × 10 = 890670
Step 2 - Add the number itself to the result
=> 890670 + 89067 = 979737
ANSWER = 979737
MULTIPLY BY 25
To multiply any number with 25, we will
" MULTIPLY THE NUMBER WITH 100 AND DIVIDE IT WITH 4 "
EXAMPLE
MULTIPLY 15698 by 25
Step 1 - Multiply the number with 100
=> 15698*100 = 156980
Step 2- Divide it with 4
=> 1569800/4 = 392450
ANSWER = 392450
MULTIPLICATION OF NUMBER CLOSE TO 100,1000 ...
Step 1 - Take base as 100 and find the distance of the numbers from 100.
Step 2 - Add the distances of the numbers by considering signs of the numbers and add the result to 100 and put two zeros to the right side of the number
Step 3 - Now, Multiply the distances of the numbers and add to the result of step 2.
Step 4 - Add the values of Step 3 and Step 4.
Lets understand this technique with the help of example :
Multiply 92 × 97
In case of 1000, take base as 1000 and remaining steps will remain the same.
CHECKING OF MULTIPLICATION
DIGIT SUM METHOD
This method is also known as Nines Remainder Method. Digit sum of a number can be found by adding the numbers. In this, we always reduce the digit sum to single figure.
The digit sum of the number must be equal to the digit sum of the answer.
If we get both side equal. we may conclude that our calculation is correct.
EXAMPLE - 92 × 97
=> 92 × 97 = 8924
=> (9 + 2 ) × ( 9 + 7 ) = 8 + 9 + 2 + 4 ( Don't count 9's or digits having sum 9 )
=> 2 × 7 = 14 (1 + 4)
=> 5 = 5
