Question: A fast food restaurant sells chicken in orders of 6, 9, and 20.
What is the largest number of pieces of chicken you cannot order from this restaurant?
After 6 all numbers divisible by 3 can be ordered (because they can all be expressed as a sum of 6's and 9's). After 26, all numbers divisible by three when subtracted by 20 can be obtained. After 46, all numbers divisible by three when subtracted by 40 can be obtained. After 46, all numbers fit into one of these 3 categories, so all numbers can be obtained. 43 is the last number that doesn't fall into one of these categories (44 = 20 + 6 * 4, 45 = 6 * 6 + 9).
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.