The aim of this paper is to study the probability that the commutator of an arbitrarily chosen pair of elements, each from two different additive subgroups of a finite noncommutative ring equals a given element of that ring. We obtain several results on this probability including a computing formula, some bounds and characterizations. Proposition 2.1. Let S and K be two additive subgroups of R and r ∈ [S, K]. Then, Pr r (S, K) = Pr −r (K, S). However, if 2r = 0, then Pr r (S, K) = Pr r (K, S). 1850023-2 Asian-European J. Math. Downloaded from www.worldscientific.com by MONASH UNIVERSITY on 04/23/17. For personal use only. A generalization of commuting probability of finite rings Proof. Let X = {(s, k) ∈ S×K : [s, k] = r} and Y = {(k, s) ∈ K ×S : [k, s] = −r}.It is easy to see that (s, k) → (k, s) defines a bijective mapping from X to Y . Therefore, |X| = |Y | and the result follows.Second part follows from the fact that r = −r if 2r = 0.Proposition 2.2. Let S i and K i be two additive subgroups of finite noncommutative rings R i for i = 1, 2, respectively. If (r 1 , r 2 ) ∈ R 1 × R 2 , then s 2 ), (k 1 , k 2 )] = (r 1 , r 2 )}. Then, ((s 1 , k 1 ), (s 2 , k 2 )) → ((s 1 , s 2 ), (k 1 , k 2 )) defines a bijective map from X 1 × X 2 to Y . Therefore, |Y | = |X 1 ||X 2 | and hence the result follows.
1850023-3Asian-European J. Math. Downloaded from www.worldscientific.com by MONASH UNIVERSITY on 04/23/17. For personal use only.