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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

1496.0. "A set problem" by HGRD01::JOSEPHCHEUNG () Tue Sep 24 1991 01:43

Hi,

	My friends asked me the following and I got no idea to solve it. So

I need some help. The problem is :

There are two sets x and y

x = {0, 1, 2} X {0, 1, 2, 3, 4} X {0, 1, 2, ..., 6}

y = {0, 1, 2, 3, ..., 104}

Now, there is an operator || such that

	|x | = |y |

What is this operator || ?

	Can anyone help me ? Thank you

-- Joseph
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1496.1UNTADC::TOWERSTue Sep 24 1991 07:545
    There are 3x5x7 = 105 elements in set X and 105 elements in set Y.
    
    |X| is the number of elements in set X.
    
    Brian
1496.2another possibilityCORREO::BELDIN_RPull us together, not apartTue Sep 24 1991 11:111
    Or a linearization mapping.
1496.3HANNAH::OSMANsee HANNAH::IGLOO$:[OSMAN]ERIC.VT240Thu Sep 26 1991 17:5414
This seems like one of those ill-defined-not-thought-out problems that
should be take out and shot.

The first digit in each set is "0" so why can't an answer be

	|S| = first-digit appearing in first element of the set

For that matter, why can't we just say

	|S| = 7

That definition certainly produces the same value for sets X and Y, namely
7.

1496.4VAXRT::BRIDGEWATEREclipsing the pastFri Sep 27 1991 14:419
>The first digit in each set is "0" so why can't an answer be
>
>	|S| = first-digit appearing in first element of the set

Sets are usually not taken to be ordered sets unless stated explicitly.

However, I agree with you that this problem is not well-defined.

- Don
1496.5trivia commentSTAR::ABBASIFri Sep 27 1991 15:221
    if a set is ordered, it is called a list.