On the equivalence between the existence of n-kernels and n-cokernels

Abstract We give an elementary proof of the statement that if an idempotent complete preadditive category has weak kernels and weak cokernels, then it has n -kernels if and only if it has n -cokernels, where n is a nonnegative integer. As a consequence, elementary proofs of two results concerning the equality between the global dimensions of certain right and left module categories are obtained.