What’s the interval of decreasing?

You are a clerk at convenience store. a customer owes 11.69 for a bag of potatoes chips. she gives you a five dollar bill. how much change should the customer receive?

How many square centimeters of wrapping paper will be used to wrap the shoe box?

You work in a hospital that has 9 floors. you need to see 3 patients on each floor. how many patients do you need to see in all?