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If the speed of X meters per second is equivalent to

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 Post subject: If the speed of X meters per second is equivalent to
 Post Posted: Thu Apr 10, 2008 11:21 pm 
If the speed of X meters per second is equivalent to the speed of y kilometers per hour, what is Y in terms of x?

5x/18

6x/5

18x/5*

60x

2,600,000x
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Steve G
 Post subject:
 Post Posted: Thu Apr 10, 2008 11:36 pm 
They're trying to trick you by giving you inconsistent units.

So perform dimensional analysis to get the same units on both sides and then solve for Y.

Ok I tried typing it out here, but it's just to time consuming to type out formula's here. Eaiser to use MS Equation Editor:
Image
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RonPurewal
 Post subject:
 Post Posted: Mon Apr 14, 2008 4:05 am 
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ManhattanGMAT Staff


Posts: 7146
best way to solve problems like this one - in which there are UNDETERMINED VARIABLES (meaning that not only are they unknown, but you actually CAN'T find specific values for them) - is to plug in sample numbers for the variables, and solve the problem with the more specific numbers in place.

so:
try x = 2
then we have 2 meters per second
which is 2 * 3600 = 7200 meters per hour (since there are 3600 seconds in an hour)
which is 7200 / 1000 = 7.2 kilometers per hour (since there are 1000 meters in a kilometer)
therefore:
if x = 2, then y = 7.2

now all you have to do is plug x = 2 into the answer choices, and see which of the choices gives 7.2.
a = 10/18
b = 12/5
c = 36/5 = 7.2
d = 120
e = 5,200,000

therefore, answer = c
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GMAT
 Post subject:
 Post Posted: Fri Jan 09, 2009 8:38 am 
See this is a very simple question

If the speed is Y km/hr and we have to change it to m/sec
then we ll multiply Y by 1000/3600, which is 5Y/18
Now if x is equivalent to Y which means Y can be written as 18X/5

X = 5Y/18
=> Y = 18X/5
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RonPurewal
 Post subject:
 Post Posted: Fri Jan 09, 2009 9:36 am 
Offline
ManhattanGMAT Staff


Posts: 7146
GMAT@23 wrote:
See this is a very simple question

If the speed is Y km/hr and we have to change it to m/sec
then we ll multiply Y by 1000/3600, which is 5Y/18
Now if x is equivalent to Y which means Y can be written as 18X/5

X = 5Y/18
=> Y = 18X/5


correct.

if you don't know how to do this, check out this site; these sorts of problems seem to be on the rise these days.

nevertheless, ALL test takers should be flexible enough to employ the aforementioned plug-in techniques if they don't happen to agree with your contention that this problem is, as you put it, "very simple".
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