Question 54907
Jose is on an elevator on the top floor of a building. Ellie is on the bottom floor elevator. They push the button at the same time to travel in opposite directions. The up elevators travels at 15 mph and the down elevators travels at 20 mph. Each floor of the building is 10 feet high. On what floor will the two pass each other?

You have to know how many stories high the building is, but here's the method using a 100 story building, (1000 ft high)
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Seems like converting the speed to feet per second would be helpful
Using 5280 ft in a mile and 3600 sec in 1 hour.
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15 mph = 15*5280/3600 = 22 ft/sec
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20 mph = 20*5280/3600 = 29.3 ft/sec
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We know that together they will have traveled 1000 ft when they pass each other
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Find out how many seconds (t) will elapse when they pass and we can use that to find what floor this occurs:
    22t + 29.3t = 1000
          51.3t = 1000
              t = 1000/51.3
              t = 19.5 secs will elapse when they pass
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Upward elevator will have traveled 22*19.5 =  429/10 ~ 43rd floor
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Downward elevator will have traveled 29.3*19.5 = 571/10 ~ 57 floors from the top