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Stefan Kohl
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Let $G$ be a group of orderorder $n$ and $d$ a positive divisor of $n$. Can we sayIs it true that there exists a subgroup of $G$ with order $d$ or $n/d$  ?

Of course this does not hold in full generality. -- In particular one quickly finds that e.g. ${\rm PSL}(2,8)$, ${\rm PSL}(2,11)$, ${\rm PSL}(2,13)$, ${\rm SL}(2,11)$, ${\rm SL}(2,13)$, ${\rm PSL}(2,17)$, ${\rm A}_7$, ${\rm PSL}(2,19)$, ${\rm A}_5 \times {\rm A}_5$, etc. are counterexamples.

Though does the assertion hold for

  • solvable groups?

  • solvable groups with derived length less than a certain bound $> 2$?

  • groups whose order has at most 2 distinct prime divisors?

A quick computation with GAP shows that any counterexample must have order $\geq 192$.

Let $G$ be a group of order $n$ and $d$ a positive divisor of $n$. Can we say there exists a subgroup of $G$ with order $d$ or $n/d$  ?

Let $G$ be a group of order $n$ and $d$ a positive divisor of $n$. Is it true that there exists a subgroup of $G$ with order $d$ or $n/d$?

Of course this does not hold in full generality. -- In particular one quickly finds that e.g. ${\rm PSL}(2,8)$, ${\rm PSL}(2,11)$, ${\rm PSL}(2,13)$, ${\rm SL}(2,11)$, ${\rm SL}(2,13)$, ${\rm PSL}(2,17)$, ${\rm A}_7$, ${\rm PSL}(2,19)$, ${\rm A}_5 \times {\rm A}_5$, etc. are counterexamples.

Though does the assertion hold for

  • solvable groups?

  • solvable groups with derived length less than a certain bound $> 2$?

  • groups whose order has at most 2 distinct prime divisors?

A quick computation with GAP shows that any counterexample must have order $\geq 192$.

Post Closed as "Not suitable for this site" by user6976, Andrey Rekalo, David White, Derek Holt, David Roberts
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A question about finite groups (a weak version of the converse of Lagrange theorem)

Let $G$ be a group of order $n$ and $d$ a positive divisor of $n$. Can we say there exists a subgroup of $G$ with order $d$ or $n/d$ ?