<![CDATA[Math Is Fun Forum / nice fact]]> 2014-05-03T16:28:55Z FluxBB http://www.mathisfunforum.com/viewtopic.php?id=12551 <![CDATA[Re: nice fact]]> no. not much. but it is the pi'th kernel

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http://www.mathisfunforum.com/profile.php?id=95904 2014-05-03T16:28:55Z http://www.mathisfunforum.com/viewtopic.php?pid=311653#p311653
<![CDATA[Re: nice fact]]> I hear it doesn't make much of a difference.

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http://www.mathisfunforum.com/profile.php?id=97578 2014-05-03T16:05:35Z http://www.mathisfunforum.com/viewtopic.php?pid=311650#p311650
<![CDATA[Re: nice fact]]> Cool Fact: The lastest kernel is kernel 3.14

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http://www.mathisfunforum.com/profile.php?id=95904 2014-05-03T13:24:58Z http://www.mathisfunforum.com/viewtopic.php?pid=311604#p311604
<![CDATA[Re: nice fact]]> Hi soroban,

soroban wrote:

. .

. .

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I tested this in Excel...which found that it is true for 3645 of the 9000 numbers in the range 1000 to 9999.

I didn't try to weed out multiples of 1111 (or anything else).

Found by Excel:
5-digit results
10890: 3645 times
10989: 640 times

Example: 8991 - 1998 = 6993: 6993 + 3996 = 10989
I haven't tried to work out why, but of the numbers that I checked the middle two digits were always 99.

4-digit results
9999: 2880 times
1170, 1251, 1332, 1413, 1494, 1575, 1656, 1737, 1818 & 1998: a total of 3815 times

3-digit results
261, 342, 423, 504, 585, 666, 747 & 828: a total of 648 times

2-digit results
99: 162

1-digit results
Zero: 90

The digit-sum of the above multiple-digit numbers always reduces to 9: eg,
(a) 10989's digit-sum is 27, whose digit-sum is 9
(b) 9999's digit sum is 36, whose digit-sum is 9
(c) 747's digit sum is 18, whose digit-sum is 9

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http://www.mathisfunforum.com/profile.php?id=40741 2009-08-12T10:41:49Z http://www.mathisfunforum.com/viewtopic.php?pid=117203#p117203
<![CDATA[Re: nice fact]]> Hi Farah;

It also works on 5 digit numbers:

Again the right hands side is divisible by 9.

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http://www.mathisfunforum.com/profile.php?id=33790 2009-08-11T22:34:34Z http://www.mathisfunforum.com/viewtopic.php?pid=117171#p117171
<![CDATA[Re: nice fact]]>

. .

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http://www.mathisfunforum.com/profile.php?id=6976 2009-08-11T22:21:52Z http://www.mathisfunforum.com/viewtopic.php?pid=117170#p117170
<![CDATA[Re: nice fact]]> farah345 wrote:

The answer will always be 9. Can someone prove how?

1111-1111 = 0

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http://www.mathisfunforum.com/profile.php?id=2143 2009-08-11T21:35:02Z http://www.mathisfunforum.com/viewtopic.php?pid=117159#p117159
<![CDATA[Re: nice fact]]> Il give you some tips. First prove that the first number (4-digit minus reverse) is divisible by 9. We know (or you can prove that too) that a number is divisible by 9 iff its sum of digits is divisible by 9. So when we first add the digits it must be a number divisible by 9. What possible numbers are there?

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http://www.mathisfunforum.com/profile.php?id=4486 2009-08-11T15:33:10Z http://www.mathisfunforum.com/viewtopic.php?pid=117149#p117149
<![CDATA[Re: nice fact]]> Hi Farah;

represent the 2 numbers like this.

As you can see the expression on the right hand side is divisible by 9.
Any number that is divisible by nine when you add its digits they will sum to 9.

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http://www.mathisfunforum.com/profile.php?id=33790 2009-08-11T15:29:25Z http://www.mathisfunforum.com/viewtopic.php?pid=117148#p117148
<![CDATA[nice fact]]> Take any 4-digit number, and its reverse, and subtract the two. For example,

7694-4967=2727

Now add all the digits:

2+7+2+7=18
1+8=9

The answer will always be 9. Can someone prove how?

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2009-08-11T15:15:20Z http://www.mathisfunforum.com/viewtopic.php?pid=117146#p117146