Please help and explain

it's urgent

Describe all the numbers that when rounded to the nearest thousand are 645,000

Each of the walls of a room with square dimensions has been built with two pieces of sheetrock, a smaller one and a larger one. the length of all the smaller ones is the same and is stored in the variable small. similarly, the length of all the larger ones is the same and is stored in the variable large. write a single expression whose value is the total area of this room. do not use any method invocations.

Pat listed all the numbers that have 15 as a multiple write the numbers in pats list