How much would it cost to cover the entire land area of united states (including alaska and hawaii) with dollar bills?

So this would be a simple problem ... if they gave you some more information. It looks like you need to know how big the area of the USA is. Also you will need to know the area of a dollar bill. Since you will probably get these numbers in different units you will most likely need to use some conversion factors. I'd google these two values and see what you can do with them

As newton's first law states a object in motion stays in motion