Abstract Algebra: Theory and Applications · Problem 15.4.5
Rings — Thomas Judson
Mathematics — Abstract Algebra · sylow-theorems
Problem
Prove that no group of order 96 is simple.
Hint. Since ∣G∣=96=25⋅3, G has either one or three Sylow 2-subgroups by the Third Sylow Theorem. If there is only one subgroup, we are done. If there are three Sylow 2-subgroups, let H and K be two of them. Therefore, ∣H∩K∣≥16; otherwise, HK would have (32⋅32)/8=128 elements, which is impossible. Thus, H∩K is normal in both H and K since it has index 2 in both groups.