Question 329572
An office building has 33 floors, each 10 feet high, and elevators that travel at a constant speed.
  If it takes 10 seconds for an elevator to go from the first floor to the fifth floor, 
how long will it take an elevator to go from the fifth floor to the middle floor?
:
"it takes 10 seconds for an elevator to go from the first floor to the fifth"
therefore
40 ft in 10 sec; that's 4 ft/sec
:
Middle floor is the 17th
17 - 5 = 12 floors
that's
10 * 12 = 120 ft
then
120/4 = 30 seconds