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by MartyMurray » Fri Dec 05, 2014 8:03 pm
This is just a conversion. Here's one way to do it.

First x is meters and y is kilometers. For every kilometer there are 1000 meters.

So first I just figure if x were meters per hour x would be 1000y per hour. Get it? If y is 3 kilometers per hour, then x would be 3000 meters per hour. Same thing. If x is meters per hour, then x = 1000y

The only thing is x is not per hour, but per second. There are 60 x 60 = 3600 seconds in each hour. So there are 3600x per hour.

So to get the formula to take into account that x is meters per second, we need to divide by 3600.

So x = 1000y/3600 and y = 3600x/1000 = 36x/10 = 18x/5
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by [email protected] » Fri Dec 05, 2014 11:49 pm
Hi chacha0212,

This question can be solved in a couple of different ways; you can use unit conversions or you can use TEST IT. Here's how I solved it:

We're asked to convert X meters/second into Y kilometers/hour....

If X = 2, then...

2 meters/second =
120 meters/minute =
7200 meters/hour =
7.2 kilometers/hour

So we need an answer that equals 7.2 when X = 2

Plugging 2 into each of the answers gives us...

A) 10/18 = 5/9
B) 12/5 = 2.4
C) 36/5 = 7.2
D) 120
E) 7,200,000

Final Answer: C

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by GMATGuruNY » Sat Dec 06, 2014 4:22 am
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 ?[/b]

(A) 5x/18
(B) 6x/5
(C) 18x/5
(D) 60x
(E) 3,600,000x
Plug in for x a value that is easy to convert from meters to kilometers.

Let x = 1000 meters per second.
Since 1000 meters = 1 kilometer, the rate = 1 kilometer per second.
Since there are 3600 seconds in an hour, 1 kilometer per second = 3600 kilometers per hour.
Thus, y = 3600. This is our target.

Now plug x = 1000 into the answer choices to see which yields our target of 3600.
Only C works:
18x/5 = (18*1000)/5 = 3600.

The correct answer is C.
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by Mathsbuddy » Fri Dec 19, 2014 6:48 am
(A) 5x/18
(B) 6x/5
(C) 18x/5
(D) 60x
(E) 3,600,000x

x m/s = y km/h
So y = xm * h / (s * km)

But 1 hour = 60 x 60 seconds = 3600s
and 1km = 1000m

So:
y = xm * 3600s / (s * 1000m)
y = x * 18 /5
ANSWER C
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by Matt@VeritasPrep » Mon Dec 22, 2014 12:35 pm
To go from x meters/sec to y/kilometers per hour, we need to know two conversions.

First, there are 1000 meters per kilometer. This means we'll be DIVIDING by 1000 to go from meters to kilometers, since every 1000 meters translates to 1 kilometer.

Second, there are 3600 seconds per hour, this means we'll be MULTIPLYING by 3600 to go from seconds to hours, since every 1 second translates to 1/3600 of an hour.

Our answer is thus x * (3600/1000), or x * (18/5).
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