Answer:
Her mistake was that she should have used –1 for moving below the lobby.
Step-by-step explanation:
Lets denote the lobby as Floor zero (0)
- if you go up, you add a positive value to this quantity.
- if you go down, you add a negative value to this quantity.
Lets assume that moving through each floor is equivalent to advancing one unit
* She first took an elevator one floor down
(-1)
Then she took the elevator back up 5 floors to her office
(+5)
Her movement is described by the expression
(-1) + (5)
Her mistake was that she should have used –1 for moving below the lobby.
