An elevator went up 15 floors, down 9 floors, up 11 floors, and down 19 floors. Find the net change. Show work using a number line.

Start at zero on your number line.

To add 15 floors, we count up to 15. (0+15=15)

Then we go down 9 floors ... count 9 down and you'll get to 6. (15-9=6)

Then we go up 11 floors ... count up 11 and you'll get to 17. (6+11=17)

Then down 19 floors ... count down 19 and you end up at - 2. (17-19=-2)

The net change is 2 floors down.