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Jul
14
comment Ways to make change
Oh, I changed the code.
Jul
14
revised Ways to make change
deleted 377 characters in body
Jul
14
comment Ways to make change
Oh, it's only up to 17^2?
Jul
14
comment If $A$, $B$ are $3\times 3$ matrices, and all elements are different from each other and greater in their absolute value than 3, then is $AB \ne 0$?
+1 for explaining the though process involved.
Jul
14
comment If $A$, $B$ are $3\times 3$ matrices, and all elements are different from each other and greater in their absolute value than 3, then is $AB \ne 0$?
Thanks, this did the trick.
Jul
14
comment If $A$, $B$ are $3\times 3$ matrices, and all elements are different from each other and greater in their absolute value than 3, then is $AB \ne 0$?
so we can take any ring?
Jul
14
comment A positive integer is equal to the sum of digits of a multiple of itself.
I think that's different Lucian. In your source we want $kn$ to have the same digit sum as $n$. In the question we want the sum of digits of $kn$ to be $n$.
Jul
14
revised Ways to make change
added 57 characters in body
Jul
14
revised Is $1 : 7 = 1 / 8$ or is it $1/7$?
deleted 1 character in body
Jul
14
comment A positive integer is equal to the sum of digits of a multiple of itself.
@zero I tried to find something but I can't see hoe to reach a contradiction.
Jul
14
asked A positive integer is equal to the sum of digits of a multiple of itself.
Jul
14
revised Ways to make change
added 195 characters in body
Jul
14
comment Ways to make change
I don't think a closed formula is known
Jul
14
answered Ways to make change
Jul
14
answered Is $1 : 7 = 1 / 8$ or is it $1/7$?
Jul
14
revised Graph where every vertex has degree 3, perfect matching?
edited body
Jul
13
comment Graph where every vertex has degree 3, perfect matching?
oh, no. I wrote a hole proof myself because I thought this comment was hinting at the Petersen graph being a counterexample, which would not be true. Apparently this result is known as Petersen's theorem !
Jul
13
answered Graph where every vertex has degree 3, perfect matching?
Jul
13
comment non-cyclic example that there is an element not contained in any maximal subgroup
Oh right, $\mathbb Z_(p^\infty)$ my teacher always talked about this while I played on my phone :(
Jul
13
answered Find the least positive integer with $24$ positive divisors.