### Home > MC1 > Chapter 4 > Lesson 4.1.2 > Problem 4-18

4-18.

. ELEVATOR CHALLENGE

Juan got on an elevator at the middle floor of a building, went up 4 floors, down 3 floors, up 1 floor, and down 9 floors, where he left the elevator on the ground floor. Homework Help ✎How many floors are in the building?

**Explain**how you found the number of floors.

First, draw a vertical number line and pick a tick mark to represent the middle floor.

Then trace his path, starting at the middle floor and move 4 floors up.

Then move 3 floors down.

Next is 1 floor up.

Last, move 9 floors down to the ground floor.

If you stop on the first floor and there are seven floors

below the middle floor, there should be 7 floors above.

How many floors are there?

Did you work backwards?

Or did you set up a number line?