Cheryl climbed a set of stairs and stopped at the middle step. She then walked down 2 steps, up 4 steps, down 3 steps, and up 5 steps, and she was at the top of the stairs. How many steps are in the set of stairs?
We know that Cheryl was at the middle of the set of stairs. Let the middle step be
Since she walked down 2 steps, that can be modelled as
We continue modelling it, until we get
Therefore, from the middle of the set of stairs to the top, there are 4 steps. That means that since
Therefore, including the middle step, we have