Special Cases of Multiplication II

Multiplication by 11

a) Multiplication by 11 of any two digit number, whose sum of the digits is less than 10

i) 63 x 11 = 693

In such multiplication we do not carry out any multiplication but simly put the sum of the digits of multiplicand between it digits.

Hence, the unit’s place digit is 3  and ten’s place digit is 6  we put 9 ( 6 + 3 ) in between 6 and 3 to get 693

ii) 72 x 11 = 7 (ten’s place digit) 9 ( 7 + 2 ) 2 (ten’s place digit) = 792

b) Multiplication by 11 of any two

digit number, total of whose digits is

more than 10.

If the sum of the digits of multiplicand is more than 10 then put unit’s place digit of multiplicand as unit’s place digit of product and add the ten’s place dgit to the multiplicand and put this sum to the left of unit’s place digit of the multiplicand to get the final product.

i) 89 x 11 =

The sum of 8 and 9 is 17 so write 7 next to unit’s place digit i.e 9. latter carry on 1 and add it to the ten’s place digit i.e 8 + 1 = 9, put it next to 7.

89 x 11 = 979

ii) 78 x 11 = (7 + 1) 1 is carried on after adding 7 + 8 = 15 / 5 ( 7 + 8 = 15) / 9 ( units place digit.

Magic with Maths / Part 2

Magic Number 12345679

 

Ask a friend for a number from 1 through 9.

In Your head, multiply your friend’s number by 9.

Multiply the magic Number by this number.

 

 

Let Your friend’s number be ‘2’

2 x 9 = 18

Tell your friend to multiply magic Number 12345679 by 18

 

12345679 x 18 = 222,222,222

You wil always get the repetition of your friend’s number. Perplex him by doing so.

Singleton.

Singleton
Singleton of a number is a single digit number which you get after adding all the digits of that number , if the resultant is not a single digit number than you again add it back.
Ex :
Singleton(23453) = 2+3+4+5+3 = 17 => 1+7 => 8
Singleton(343) = 3+4+3 = 10 => 1 + 0 => 1
Singleton(534533256) = 9 or 0
Note : While calculating the Singleton , you can banish those numbers which add up to 9 , Remember : Singleton(9+x) = Singleton(x)
So when you find Singleton(918754) , you can ignore
– 9
– 8 and 1
– 4 and 5
so , you are left with 7 , which is the Singleton