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## #1 2013-01-21 05:13:22

cooljackiec
Member
Registered: 2012-12-13
Posts: 185

### probability and counting??

How many 20-digit numbers are such that the sum of their digits is even?

I see you have graph paper.
You must be plotting something

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## #2 2013-01-21 06:42:14

muxdemux
Member
Registered: 2012-12-23
Posts: 80

### Re: probability and counting??

I could only figure out that there's at least

.

Last edited by muxdemux (2013-01-21 06:42:30)

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## #3 2013-01-21 09:25:37

cooljackiec
Member
Registered: 2012-12-13
Posts: 185

### Re: probability and counting??

That doesn't help, I knew that just that i keep losing count.

I see you have graph paper.
You must be plotting something

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## #4 2013-01-21 13:24:26

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 106,437

### Re: probability and counting??

Hi;

You do not have to do much counting. Spot the pattern works well here.

I am getting 4.5 x 10 ^19 numbers.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.

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## #5 2013-01-22 12:02:13

cooljackiec
Member
Registered: 2012-12-13
Posts: 185

### Re: probability and counting??

Thank you

I see you have graph paper.
You must be plotting something

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