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Elevator Problem

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31 Jan 2004, 22:13
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

How to solve for the following? This was on the Kaplan practice test on their website. I may have mixed up some of the numbers used.

Jill gets on the elevator on the 11th floor and will take it up at a rate of 59 floors per minute. John gets on the elevator on the 63rd floor and will take the elevator down at 53 floors per minute. What floor will they meet?

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31 Jan 2004, 22:19
Solve for x.

Answer = 11 + 59x = 63 - 53x
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01 Feb 2004, 01:58
Zhung,

I found the exact numbers:

Jill starts on 11th floor and goes up 57 floors/minute
John gets on at 51st floor and goes down 63 floors/minute.

The equation would be:

11+57x = 51-63x

x = 1/3

That does not make sense. Please clarify. Thanks.
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01 Feb 2004, 02:05
norbertackerman wrote:
Zhung,
11+57x = 51-63x
x = 1/3

Answer = 11+(57/3) = 30 = 51 - (63/3)
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01 Feb 2004, 02:11
Zhung,

awesome. I see. Thank you!
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01 Feb 2004, 12:27
In these kinds of question you have to equate one and only parameter. The time taken to travel.
The difference between two people is 51-11 = 40 floors
If both of these meet at some floor then person at lower floor would have travelled x floors in time t and in the same time t the other person would have travelled 40-x floors down

so t = x/57 = ((40-x)/63
63x = 40*57-57x
so x = 40*57/ 120 = 19
so the person at lower floor travels 19 floors up which is 11+19 = 30th floor.
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02 Feb 2004, 11:40
anandk

how did you comeup with the diff of 40 floors.

the Question says 11th floor and 63rd floor so the diff shoule be 63-11=52. and I could not get the answer.

Usually what I do is I compute the the rate when they travel together in this case 59+53 = 112 and compute the time. They travel 52 floors at the rate of 112 so the time will be 56/112. From this you can compute the number of floors one person travles when they meet.
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02 Feb 2004, 11:43
You are right. norbertackerman has corrected his question somewhere down the line.
02 Feb 2004, 11:43
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