Pam gets on an elevator at the 12th floor of a building going up. Hila

Question

Pam gets on an elevator at the 12th floor of a building going up. Hilary gets on an elevator on the 63rd floor at the same time in the same building going down. At what floor will their paths cross?
 
(1) Pam's elevator is moving at a rate of 4 floors per second.
(2) Hilary's elevator is moving at a rate of 5 floor per second.

rohit8865 · Answer

the floor will their paths cross = distance/relative speed

since nowhere mentioned the floor are equally spaced, we cannot calculate their meeting point

Ans E

SI777 · Answer

if we take the difference in floors. there are 51 floors btw them and we can find the intersection floor by the formula = dist btw them / speed of pam + speed of hillary

any thoughts ?

Diwakar003 · Answer

Your solution will work if we assume the elevators doesn't stop anywhere. Nowhere it is mentioned that the elevators doesn't stop. We have no idea which elevator stops for how much time so it's impossible to find when the elevators will meet. Ans E.

Cheers!

chetan2u · Answer

Hi

We should not read too much in a Q and make it more complicated...

The floors have to be equally spaced and the you should not assume on whether it stops or not. It is clearly given that it is moving at a certain speed. Stoppages or not, they will be included 
So the answer is C, as we get the combined speed and distance between them

C

tapabrata · Answer

Pam is on 12th floor and Hilary is on 63rd floor. So number of floors between them = 63-12-1=50

With each statement alone, we cannot determine the floor at which they cross as we do not know the speed of the other elevator.

Taking statements 1 and 2 together we get Relative speed = 9 floors/s

So time required to cover 50 floors = 50/9 s
After 50/9 secs, the elevators will just cross each other ( the top of Pam's elevator and the bottom of Hilary's elevator)

Number of floors covered by Pam's elevator in 50/9 secs = 4*50/9~ 22 2/9 floors.
So that means Pam's elevator has covered 22 floors and entering the next floor which is 12+22+1= 35th floor. At the same time Hilary's elevator has already crossed the 36th floor and entering the 35th floor. Thus their paths cross on the 35th floor.

Answer is C

bumpbot · Answer

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Pam gets on an elevator at the 12th floor of a building going up. Hila

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