Beauty of “9”

Beauty of “9”

The Number 9 is a very interesting number in Arithmetic, Number Theory, Mathematics rather anything which involves some calculations.

We have many articles on Numbers, and I am sharing something which I studied many years ago but refreshing to make Numbers user friendly to my daughter in school.

Digit Sum:

The Digit Sum is a single digit number.

It is calculated by adding the digits in a number, adding again if necessary till we have a single digit.

For eg:

76 -> 7+6 = 13 -> 1+3 = 4 so digit sum is 4

142 -> 1+4+2 = 7 so digit sum is 7

We will see usage of Digit Sum later, but at the moment it suffices to say, any large number can be reduced to its digits sum which is single digit.

Let us see the beauty of Number 9.

If we have 9 in any number, we need not consider it in addition to find digit sum as 9 does not change the digit sum.

For eg:

91 -> 9+1 = 10->1+0 = 1 so digit sum is 1, same as discarding 9 from number

139 ->1+3+9 = 13-> 1+3 = 4 so digit sum is 4, same as discarding 9 and adding 1 and 3

This is interesting and implies , we can discard any combination which sums 9 and calculate digit sum of large numbers quickly.

For eg:

1724 , we see 7 and 2 will sum to 9 so we discard and find digit sum as 1+4 = 5

45981, we see 9 can be discarded and so 8 and 1 as they form a 9 so digit sum is 4+5 = 9

This helps to calculate digit sum quickly for large numbers by looking at it.

We will see usage of Digit Sum later but this is big help for all those who believe in Numbers and Magic of Numbers while selecting Mobile Number, Lottery Number or Car Number or all those Number Lovers who are calculating to find Digit Sum to match with Birthday, Calendar Day etc

It is FAST, FASTER and FASTEST…….

Selecting Mobile Number so it matches with your Birth Date you have to select from many, you have to add 10Digit Numbers…….Use the Above…..Go Ahead

For eg:

9840218279…….we discard Ist,6th, 7th 8th , 9th and Last Digit quickly as they have 9 or pair which makes 9

We add 8+4+0+2+1 = 15-> 1+5 = 6

This is one interesting way to keep young children busy and show them how to do faster……they love it!

So all the parents like me, who have challenge to keep young children occupied while car drive or train journey or while watching news……keep throwing such 5, 10 ,15 20 digit numbers at them…….and keep telling they get remote or popcorn only when they do sum faster then you……

Do share the secret later…..You sure will get a Big Hug or Punch 🙂