Since the actual height of each step isn't specified, I'll use the units of ft/step. And the unit should indicate to you that division is involved. So:
Modis building:
15 feet / 22 steps = 15/22 feet/step ≠0.681818182 ft/step
Sears Tower
7 feet / 17 steps = 7/17 feet/step ≠0.411764706 ft/step
On a side note, the stair dimensions are completely unrealistic since the international standard for stairs requires the tread depth to be a minimum of 11 inches. And the tread depth mentioned is respectively 8.18" and 4.94" which are both way too shallow.
