[Math] Isomorphic groups but not isomorphic rings

abstract-algebraexamples-counterexamplesring-theory

Provide an example of two rings that have the same characteristic, are isomorphic as groups but are not isomorphic as rings.
I'm confused with how to being. I know that having the same characteristic means that the concatenation is the same number to receive the zero element.

Best Answer

$\mathbb{R} \times \mathbb{R}$ and $\mathbb{C}$ are isomorphic as additive abelian groups but they have a different multiplicative structure