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GMAT Prep ?? (Carlos Average Speed)

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GMAT Prep ?? (Carlos Average Speed)

by dferm » Fri May 09, 2008 6:52 am
If it took Carlos 1/2 hour to cycle from his house to the library yesterday, was the distance that he cycled greater than 6 miles? (Note: 1mile = 5,280)

(1) The average speed at which Carlos cycled from his house to the library yesterday was greater than 16 feet per second.

(2) The average speed at which Carlos cycled from his house to the library yesterday was less than 18 feet per second.

Can someone help... I answered this question correctly but can setup up equation..

Thanks..
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by amitansu » Fri May 09, 2008 10:10 pm
Ans E.

From 1: x> 16ft/s (x assumed speed)
not sufficient no upper limit...

from 2: x< 18ft/s
not sufficient, no lower limit..

combining both, 16<x<18> 6*5280=31680 ft ?

if taken 16.1 then, 16.1*30*60=28980 <31680> 31680 so insufficient.
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by jsl » Mon Nov 03, 2008 3:13 pm
Given the time, anyone could do this question. However, since this is the GMAT, I'm sure that the testmakers will have written in a shortcut and they will not expect you to do time-consuming maths.

Can anyone spot the shortcuts?
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by jimmiejaz » Mon Nov 03, 2008 4:05 pm
jsl wrote:Given the time, anyone could do this question. However, since this is the GMAT, I'm sure that the testmakers will have written in a shortcut and they will not expect you to do time-consuming maths.

Can anyone spot the shortcuts?
Hi,
As speed is directly proportional to ditance, if he needs to travel more than 6 miles, his speed should be more than 6/.5 = 12 miles/hr.

=> 12*5280/60*60 = 88/5 which is little more than 17.
now chk the answers. even combined statements dont give any concrete value. so ans is E.
Hope it helps.
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by kination » Wed Apr 01, 2009 8:11 pm
Ans: E

Statement 1:

Carlos can travel at least:

16x60x60/2 (Distance traveled in ft) / 5280 (1 mile) = 5 5/11 miles

Statement 2:

Carlos can travel at MOST:

18x60x60/2 (Distance traveled in ft) / 5280 (1 mile) = 6 3/22 miles


Statement 1 is not sufficient because ">5 5/11" is not always "greater than 6".

Statement 2 is not sufficient because "<6 3/22" is not always "greater than 6"

Statement 1 and 2 together both are not sufficent because

5 5/11 < x < 6 3/22 while x is NOT always greater than 6.

Thus, both statement together are NOT sufficient.
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by GMATowned » Fri Dec 18, 2009 10:49 am
I don't understand this one. Doesn't statement two clearly state he travels less than 18? so wouldn't we test 17 ft/sec? just as in the first one it states he travels faster than 16 ft/sec so wouldn't we test the first value at 17 ft/sec? I am really confused
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by ssuarezo » Fri Dec 18, 2009 12:15 pm
GMATowned wrote:I don't understand this one. Doesn't statement two clearly state he travels less than 18? so wouldn't we test 17 ft/sec? just as in the first one it states he travels faster than 16 ft/sec so wouldn't we test the first value at 17 ft/sec? I am really confused
Hi Towned:

16<x<18 means from 16.0001 to 17.9999, however, as others tested, we get different answers if we test 16 or 18, that is, we would get a yes (distance greater than 6 miles) if we use 17.99 and a no (distance less than 6 miles) with 16.1, so none of them give us an answer. You can't just test with 17, you have to discard other values in the range to get a defnite yes or a definite no to the answer.

Thanks,
Silvia
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by bhumika.k.shah » Tue Feb 02, 2010 7:32 am
hey can u tell me how u got the 60-that i have highlighted ?

is it because u are converting it into minutes ?

i am guessing that could be the only possible reason and hence u r multiplying it with 60/2 ( since we need to find it for 1/2 an hour))

am i correct??
kination wrote:Ans: E

Statement 1:

Carlos can travel at least:

16x60x60/2 (Distance traveled in ft) / 5280 (1 mile) = 5 5/11 miles

Statement 2:

Carlos can travel at MOST:

18x60x60/2 (Distance traveled in ft) / 5280 (1 mile) = 6 3/22 miles


Statement 1 is not sufficient because ">5 5/11" is not always "greater than 6".

Statement 2 is not sufficient because "<6 3/22" is not always "greater than 6"

Statement 1 and 2 together both are not sufficent because

5 5/11 < x < 6 3/22 while x is NOT always greater than 6.

Thus, both statement together are NOT sufficient.
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by papgust » Tue Feb 02, 2010 10:38 pm
The question says 16 feet/Sec

to convert this into hour, he has multiplied by 60 twice. 16*60*60 feet/hr

That 1/2 is the time taken to travel. Distance = Speed * Time = 16*60*60*1/2
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by bhumika.k.shah » Wed Feb 03, 2010 7:05 am
yea thats what i finally figured :D
papgust wrote:The question says 16 feet/Sec

to convert this into hour, he has multiplied by 60 twice. 16*60*60 feet/hr

That 1/2 is the time taken to travel. Distance = Speed * Time = 16*60*60*1/2
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by Ferdous » Mon Oct 04, 2010 7:03 pm
Found this one in manhattangmat forum... thought it was the easiest way...

I think it helps to try to rephrase the question. Since rate * time = distance, we can translate the question as:
Is (r)(0.5) > 6?

We can manipulate this by dividing both sides by 0.5. Now it's rephrased as:
Is r > 12 mph?

Noticing that the statements are in feet/second, we should convert 12mph to ft/sec. (12mi/hr) * (1hr/3600 s) * (5280 ft/1 mi) = 5280/300 = 17.6 ft/sec.

Is r > 17.6 ft/sec?

(1) Says r > 16 ft/sec. This is insufficient. r could be less than or greater than 17.6.

(2) says r < 18 ft/sec. This is also insufficient. r could be either less than or greater than 17.6.

Putting (1) and (2) together, 16 < r < 18. We still do not know for sure that r > 17.6. The answer is (E).
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