Multiplication with 9s

H.D. Motiramani

Type 1 when Multiplier and multiplicand are of equal number or digits, For example 345*999

Type 2 when Multiplier is larger in number of digits than multiplicand, For example 34*999

Type 3 when Multiplicand is of larger number of digits than multiplier, For example 345*99

 

Type 1 when Multiplier and multiplicand are of equal number or digits, For example 345*999

Left Hand Side LHS is 345, Right Hand Side RHS is 999

Step1. Reduce 1 from LHS to make it 344.

Step2. Subtract 344 (result of step 1) from 999 to get 655

The answer will be 344655

 

One more example: 44*9.9

Make it 44*99 and in answer place the decimal point appropriately.

Step 1. Reduce 1 from LHS to make it 43

Step 2. Deduct this 43 from 99 to get 99-43= 56

The answer will come from 4356 after placing decimal appropriately to make it 435.6

 

Type2 when Multiplier is larger in number of digits than multiplicand, eg. 34*999

Step 1. Make LHS as 034 and deduct 1 to make it 033

Step 2. Deduct this 033 number from 999 to make it 966

The answer will be 033966 or 33966

 

One more example: 87*9.99

Step 1. Treat 87 as 087 and deduct 1 to make it 086

Step 2. Deduct this 086 from 999 (place decimal appropriately before arriving at answer. Get 913

Place decimal after two digits in 86913 to show the answer as 869.13

 

Type 3 when Multiplicand is of larger number of digits than multiplier, For example 345*99

Step 1. Increase the multiplier by a single digit to make it 99+1=100

Step 2. Make a simple multiplication of 345 with 100 to make it 34500

Now since this 34500 is larger than the answer, deduct 345 from 34500 to make it 34500-345=34155

 

One more example: 456*9.9

Step 1. Increase the multiplier digit 9.9 to 10.0 and use this multiplier to get 4560

             Now we have increased 9.9 by 0.1 only therefore the resultant 4560 is larger by 456*0.1=45.6

Step2.  Reduce this 45.6 from 4560 to get the answer 4560-45.6=4514.4


—00—

< Contents                                                                                                                Next >