Most people in the African countries see greeting as "Good morning ma" or "good morning sir". When you say hello ma, it sounds like an insult. Most times It sounds so funny to me, especially when it results to a fight or even malice.
"Hello ma" is as well a greeting as "Good morning ma" is. However we cannot dispute the fact that we are in Africa. So in other to avoid quarrels when you see your elder, greet by saying good morning ma or sir(smiles). Is you can prostrate, pls do because if you don't, you will still be seen as disrespectful, well it depends on your culture as well. In all, do what you can. Don't kill yourself for anybody. But be respectful the best way.