Math Is Fun Forum

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Times 4 Kidz

For times tables
from 6x6 to 9x9,
you only have to
remember the number
14.  14 is the
magic number.
14 will replace 6.
Add 9 to 14.
23 will replace 7.
Add 9 to 23.
32 will replace 8.
Add 9 to 32.
41 will replace 9.
6 is 14
7 is 23
8 is 32
9 is 41

9 x 9 = 41 + 41, almost,
but don't add the two 1's
together, multiply them.

8 x 8 = 32 + 32, but
actually multiply the 2 by
the 2 in the 32's.

7 x 7 = 23 + 23, but
multiply the 3's together
so it ends in a 9, not a 6.

9 x 8 = 41 + 32, but
do 1 x 2, not 1 + 2 for
the one's digit.

7 x 8 = 23 + 32 except
do 3 x 2, not 3 + 2.

7 x 9 = 23 + 41 except
multiply 3 x 1, not 3 + 1.

6 x 9 = 14 + 41 except
do 4 x 1, not 4 + 1.

6 x 7 = 14 + 23 except
instead of 37 add 5 more
because 4 times 3 is 5 more
than 4 + 3.

6 x 6 = 14 + 14, except
28 is not the right
answer, so add 8 more
because 4 x 4 is 8 more
than 4 + 4.

6 x 8 = 14 + 32 + 2 because
         4 x 2 is 2 more than
         4 + 2.
         
Pretty neat huh??
Learned this from some
finger trick on youtube.

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igloo myrtilles fourmis

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Times 4 Kidz

In other words

and

Neat? I think this is making it far more complicated than the original simple products – and what’s more, the complication is absolutely and totally unnecessary!!

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Times 4 Kidz

Hey, look. I have a new way of adding two numbers. To add two numbers, you simply follow these steps:

(i) multiply the two numbers
(ii) multiply the predecessors of the two numbers
(ii) subtract the second result from the first result
(iv) add 1

Example, to add 12 + 34:

(i) multiply the numbers: 12 × 34 = 408
(ii) multiply their predecessors: 11 × 33 = 363
(ii) subtract: 408 − 363 = 45
(iv) add 1: 45 + 1 = 46

Hence 12 + 34 = 46.

BUT … is it worth it? Why don't we just add 12 + 34 directly?

Precisely!

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Times 4 Kidz

A fun diversion, nonetheless

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Times 4 Kidz

Jane, your equations are very interesting and show how it works!!
Actually, the way you do this on your two hands is pretty cool,
and probably more fun than my interpretation of the finger method.
The video is kind of slow motion 8 minutes, so
that's why I didn't post it at first.
http://www.youtube.com/watch?v=YL3PtlxYkZ4
same as this click on link:
http://www.youtube.com/watch?v=YL3PtlxYkZ4

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igloo myrtilles fourmis

shocamefromebay

Member

Registered: 2007-05-30

Posts: 103

Re: Times 4 Kidz

Hey, look. I have a new way of adding two numbers. To add two numbers, you simply follow these steps:

(i) multiply the two numbers
(ii) multiply the predecessors of the two numbers
(ii) subtract the second result from the first result
(iv) add 1

Example, to add 12 + 34:

(i) multiply the numbers: 12 × 34 = 408
(ii) multiply their predecessors: 11 × 33 = 363
(ii) subtract: 408 − 363 = 45
(iv) add 1: 45 + 1 = 46

Hence 12 + 34 = 46.

BUT … is it worth it? Why don't we just add 12 + 34 directly?

Precisely!

Did i do something wrong?

a + b = (a x b) - ((a-1)(b-1)) +1
a + b = (a x b) - (ab - b - a +1 )+1
a + b = ab - ab - b - a +2
a + b = -b - a +2

Did i do something wrong?

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Times 4 Kidz

Did i do something wrong?

a + b = (a x b) - ((a-1)(b-1)) +1
a + b = (a x b) - (ab - b - a +1 )+1
a + b = ab - ab - b - a +2
a + b = -b - a +2

Did i do something wrong?

Your working is as if the second set of brackets in the second line isn't there.

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Why did the vector cross the road?
It wanted to be normal.

mason777

Member

Registered: 2007-11-05

Posts: 44

Re: Times 4 Kidz

Thats actually pretty cool:cool: I never thought of it that way. I'm doing times tables in school (im in elementary school) So i need all the help i can get

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Man, what a pain...

mason777

Member

Registered: 2007-11-05

Posts: 44

Re: Times 4 Kidz

In other words

and

Neat? I think this is making it far more complicated than the original simple products – and what’s more, the complication is absolutely and totally unnecessary!!

You shouldn't be so negative.. its not all about being smart its about being creative and finding stuff out you didn't know before. Its not nice to judge people

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Man, what a pain...

Devantè

Real Member

Registered: 2006-07-14

Posts: 6,400

Re: Times 4 Kidz

Who judged who?

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Times 4 Kidz

I'm the judge.  Everybody's awesome!!

Another way to remember that 23 goes with 7.
7 -> 77    77 + 23 = 100

Last edited by John E. Franklin (2007-12-07 17:22:40)

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igloo myrtilles fourmis