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Manager  Joined: 07 Feb 2015
Posts: 61
At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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7 00:00

Difficulty:   15% (low)

Question Stats: 79% (01:22) correct 21% (01:41) wrong based on 187 sessions

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At the rate of f floors per m minutes, how many floors does an elevator travel in s seconds?

(A) $$\frac{fs}{60m}$$

(B) $$\frac{ms}{60f}$$

(C) $$\frac{fm}{s}$$

(D) $$\frac{fs}{m}$$

(E) $$\frac{60s}{fm}$$

Explanation: You’re given a rate and a time, and you’re looking for distance. This is clearly a job for the rate formula. Since the rate is in terms of minutes and the time is in seconds, you’ll need to convert one or the other; it’s probably easier to convert s seconds to minutes than the rate to floors per second. Since 1 minute equals 60 seconds, s seconds equals $$\frac{s}{60}$$ minutes. Now we can plug our rate and time into the rate formula: $$r=\frac{d}{t}$$
$$\frac{f}{m}=d/\frac{s}{60}$$

Now, cross-multiply:

$$dm = \frac{fs}{60}$$

$$d=\frac{fs}{60m}$$, choice (A).
GMAT Club Legend  V
Joined: 12 Sep 2015
Posts: 4009
At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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gmatser1 wrote:
At the rate of f floors per m minutes, how many floors does an elevator travel in s seconds?

(A) $$\frac{fs}{60m}$$

(B) $$\frac{ms}{60f}$$

(C) $$\frac{fm}{s}$$

(D) $$\frac{fs}{m}$$

(E) $$\frac{60s}{fm}$$

Looks like a good candidate for the INPUT-OUTPUT approach.

Let's INPUT some values for f, m and s.
Let's say that f = 8 floors, m = 2 minutes, and s = 30 seconds

That is, the elevator travels at a rate of 8 floors per 2 minutes.
How many floors does an elevator travel in 30 seconds?

Well, 8 floors in 2 minutes translates to 4 floors in 1 minute, and 2 floors in 30 seconds.

So, when f = 8, m = 2, and s = 30, the answer to the question (OUTPUT) is 2 floors

Now, let's plug f = 8, m = 2, and s = 30 into each answer choice and see which one yields an OUTPUT of 2

(A) $$\frac{(8)(30)}{60(2)}$$ = 2 GREAT!

(B) $$\frac{(2)(30)}{60(8)}$$ = 1/8 ELIMINATE

(C) $$\frac{(8)(2)}{(30)}$$ = 8/15 ELIMINATE

(D) $$\frac{(8)(30)}{(2)}$$ = 120 ELIMINATE

(E) $$\frac{60(30)}{(8)(2)}$$ = some big number ELIMINATE

For more information on this question type and this approach, we have some free videos:
- Variables in the Answer Choices - http://www.gmatprepnow.com/module/gmat- ... /video/933
- Tips for the Algebraic Approach - http://www.gmatprepnow.com/module/gmat- ... /video/934
- Tips for the Input-Output Approach - http://www.gmatprepnow.com/module/gmat- ... /video/935

Cheers,
Brent
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Re: At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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f/m=floors per minute
f/60m=floors per one second
fs/60m=floors per s seconds
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Joined: 04 Mar 2011
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Re: At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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gmatser1 wrote:
At the rate of f floors per m minutes, how many floors does an elevator travel in s seconds?

(A) $$\frac{fs}{60m}$$

(B) $$\frac{ms}{60f}$$

(C) $$\frac{fm}{s}$$

(D) $$\frac{fs}{m}$$

(E) $$\frac{60s}{fm}$$

We have a rate of (f floors)/(m minutes) and need to determine how many floors an elevator travels in s seconds = s/60 minutes, and thus:

f/m x s/60 = fs/60m

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Intern  B
Joined: 10 Nov 2017
Posts: 1
Re: At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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Let's let f = 60 in m = 1 minutes as it will make the calculation easy!
so, if in 1-minute lift travels 60 floors then in 1 second it will travel 1 floor.
Plugging the values as f=60,s=1,m=1 the result should be 1
So, the answer is A!

Jkay
Non-Human User Joined: 09 Sep 2013
Posts: 13275
Re: At the rate of f floors per m minutes, how many floors does an elevato  [#permalink]

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_________________ Re: At the rate of f floors per m minutes, how many floors does an elevato   [#permalink] 13 Oct 2019, 20:17
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