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: A man lives in an apartment building on the 100th floor. He rides the elevator all the way down to floor 1 every morning then all the way up to floor 100 every evening. The elevator is coin-operated. It costs $0.25 per floor for floors 1-25, $0.50 per floor for floors 26-50, $0.75 per floor for floors 51-75, and $1.00 per floor for floors 75-100. How much money does the man spend each day riding the elevator?
Answer: The man spends $125 per day riding the elevator. It costs $62.50 each way.