Cardinality of lower triangular Matrix contains rational number

Asked Sep 30 '13 at 00:53

Active Oct 22 '13 at 14:01

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Can anybody explain what is the cardinality of lower triangular Matrix contains rational number and size of matrix is lower than $7$?

I don't have any idea where to start and what to do?

edited Oct 22 '13 at 14:01

Martin Sleziak

asked Sep 30 '13 at 00:53

Mohammad Razeghi

1

Your question doesn't make any sense to me: it looks like a collection of math words strung together almost randomly. Where did you get this question? Do you understand it yourself? Please try rephrasing and/or giving an example. If you mean "What is the cardinality of the set of all $n \times n$ matrices which are lower triangular and have rational entries, as $n$ ranges over all positive integers less than $7$", then the answer is that this a countable set, so of cardinality $\aleph_0$. – Pete L. Clark Sep 30 '13 at 04:57

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