Burj Khalifa and its floors

Irfan and Albert visited the tallest building in the world Burj Khalifa in Dubai. Irfan rides up after getting on one of the elevators on 11th floor, at the rate of 57 floors per. At the same time, Albert gets on another elevator on the 51st floor of Burj Khalifa and rides down at the rate of 63 floors per minute. At which floor will their paths cross if they continue traveling at these rates?

Solution:

Let’s suppose their paths cross after x minutes
Then, 11 + 57x = 51 – 63x
120x = 40
x = 1/3 min
The number of floors covered by Irfan in 1/3 min. = 1/3 X 57 = 19

So their paths cross at (11 + 19)^th floor = 30th floor from ground