### Home > CC1 > Chapter 7 > Lesson 7.3.4 > Problem 7-123

7-123.

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, move 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?