Steve gets on the elevator at the 11th floor of the building and rides up at a rate of 57 floors per minute. At the same time, Joyce gets on an elevator on the 51st floor of the same building and rides down at a rate of 63 floors per minute. If they continue travelling at these rates, at which floor will their paths cross?
Their approach rate is 57+63 = 120 floors per minute. They are 51-11 = 40
floors apart. Since 40 is 1/3 of 120, it'll only take 1/3 of a minute till
their paths cross. So at 57 floors per minute, in 1/3 of a minute, Steve will
go up 1/3 of 57 or 19 floors, so he'll be on the 11th+19 = 30th floor in 1/3
of a minute. That's the answer. But as a check, at 63 floors per minute, Joyce
will come down 1/3 of 63 or 21 floors, so she'll be on the 51st-21 or 30th
floor too in 1/3 of a minute. So it checks.
Answer: 30th floor.
Edwin