X gets on a lift on the ground floor which goes up at a speed of 30 floors per minute whereas Y gets on another lift at the same time on the 50th floor which goes down at a speed of 45 floors per minute. On which floor will their paths cross? (lifts are moving without stopping at any floor)
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 20th
Given that
X goes up from the ground floor at a speed of 30 floors per minute
Y goes down from the 50th floor at a speed of 45 floors per minute
Let, the time taken to cross each other be ' t ' minutes
According to the question
0 + 30t = 50 - 45t
75t = 50
t = 50/75 = 2/3 minutes
The number of floors covered by X in 2/3 minutes = 2/3 × 30 = 20
Hence, the floor at which they cross each other is = 0 + 20 = 20th