## Community Chat

Esteemed Contributor
Posts: 6,235
Registered: ‎03-09-2010

## Re: Cool Math Trick

wow! amazing

Respected Contributor
Posts: 2,483
Registered: ‎10-19-2011

## Re: Cool Math Trick

[ Edited ]

No....I do not know what numbers those are.

I did it twice....Have no idea.

-Do Not Copy Pls-
Honored Contributor
Posts: 12,804
Registered: ‎03-09-2010

## Re: Cool Math Trick

[ Edited ]

Nope, did it with 3 different phone numbers

***did it again and got it!***

Edited days later!!!

Trusted Contributor
Posts: 1,309
Registered: ‎12-01-2012

## Re: Cool Math Trick

It came out right for me.

Respected Contributor
Posts: 2,483
Registered: ‎10-19-2011

## Re: Cool Math Trick

[ Edited ]

@Lucky Charm wrote:

Nope, did it with 3 different phone numbers.

I had to use the calculator ON the phone to achieve the right answer... I could not use any calculator. My first attempt for my land line went no where.... so I used my tiny mobile phone's calculator with it's own phone number and got the right answer. Remember to do the = sign after each entry.

It was correct.....

............ETA....I was wrong again....any calculator will work.....it's the = sign after each entry that is crucial..... to arrive at the answer.

-Do Not Copy Pls-
Trusted Contributor
Posts: 1,309
Registered: ‎12-01-2012

## Re: Cool Math Trick

Here is a another cool math trick.  My dad taught me this, never heard it in school.  Maybe you can pass it on to your children/grandchildren.

A little boy was given this quiz for multiples of 9 at school:

2 x 9 =

3 x 9 =

4 x 9 =

5 x 9 =

6 x 9 =

7 x 9 =

8 x 9 =

9 x 9 =

Realizing that he did not know any of the answers, he counted them to see how many questions he was going miss:

2 x 9 = 1

3 x 9 = 2

4 x 9 = 3

5 x 9 = 4

6 x 9 = 5

7 x 9 = 6

8 x 9 = 7

9 x 9 = 8

Eight wrong answers!  That seemed like a lot, so he decided to count them again, this time from the bottom up, just make sure:

2 x 9 = 18

3 x 9 = 27

4 x 9 = 36

5 x 9 = 45

6 x 9 = 54

7 x 9 = 63

8 x 9 = 72

9 x 9 = 81

He turned in the quiz as is and got 100% A+!

The other cool thing about multiples of "9" is that the numbers in the correct answer always add up to 9!

2 x 9 = 18  (1 + 8 = 9)

3 x 9 = 27  (2 + 7 = 9)

4 x 9 = 36  (3 + 6 = 9)

6 x 9 = 54  (5 + 4 = 9)

7 x 9 = 63  (6 + 3 = 9)

8 x 9 = 72  (7 + 2 = 9)

9 x 9 = 81  (8 + 1 = 9)

Bookkeepers trick:  if your calculator tape is off by "9" or a multiple of 9, it is often due to a transposed number (for instance, entering 89 instead of 98 - the difference between a transposed number is always "9", or a multiple of 9 (98 - 89 = 9;  42 - 24 = 18; 97 - 79 = 18; 150 -105 = 45; 170 - 107 = 63)

Honored Contributor
Posts: 19,271
Registered: ‎03-09-2010

## Re: Cool Math Trick

Wow! very cool!

Honored Contributor
Posts: 65,634
Registered: ‎03-10-2010

## Re: Cool Math Trick

[ Edited ]

Very neat, both of them. I always wished I'd 'got' math instead of struggling along to fulfill requirements... It would be nice to be able to figure out and to understand why things like this work out...

In my pantry with my cupcakes...
Honored Contributor
Posts: 12,804
Registered: ‎03-09-2010

## Re: Cool Math Trick

@cbrite wrote:

@Lucky Charm wrote:

Nope, did it with 3 different phone numbers.

I had to use the calculator ON the phone to achieve the right answer... I could not use any calculator. My first attempt for my land line went no where.... so I used my tiny mobile phone's calculator with it's own phone number and got the right answer. Remember to do the = sign after each entry.

It was correct.....

............ETA....I was wrong again....any calculator will work.....it's the = sign after each entry that is crucial..... to arrive at the answer.