You have a large number of friends coming over and they all get thirsty. Your first friend asks for 1/2 a cup of water. Your second friend asks for 1/4 a cup of water. Your third friend asks for 1/8 a cup of water, etc.
How many cups of water do you need to serve your friends?
Answer: Just one. If your friends kept asking for water like this forever one cup would be enough.
Question: I'm 10 years old my brothers half my age now I'm 100 years old how old is my brother now?
Answer: 95 years old Because he's half my age when I was 10 so he's 5 years old so I'm only 5 years older 100-5=95