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If it took Carlos 1/2 hour to cycle from his house to the library yest

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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 08 Jan 2016, 14:24
Hi all,

I got this question during a CAT of the gmat prep software and I am not sure the result the softwar says is correct. It says E, while for me is B. Here is the question:

"it took Carlos 1/2 hour to cycle from his house to the library, was the distance that he cylced grater than 6 miles? (1 mile = 5,280 feet)

(1) The avrage 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.

Now, based on my calculation, with statement B we should figure out that Carlos cycled for sure less than 6 miles, so B is correct, but on the Prep software they say E is correct.

Why?

Thanks a lot
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 08 Jan 2016, 15:24
pepo wrote:
Hi all,

I got this question during a CAT of the gmat prep software and I am not sure the result the softwar says is correct. It says E, while for me is B. Here is the question:

"it took Carlos 1/2 hour to cycle from his house to the library, was the distance that he cylced grater than 6 miles? (1 mile = 5,280 feet)

(1) The avrage 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.

Now, based on my calculation, with statement B we should figure out that Carlos cycled for sure less than 6 miles, so B is correct, but on the Prep software they say E is correct.

Why?

Thanks a lot


Couple of points.

1. Make sure to follow ALL posting guidelines (link in my signatures). Search for a question before you post a new thread. This and many other questions should have been already discussed on GMATCLUB. Merged the topics. Refer above for the solution.

2. For any official questions (official guides, GMATPREP) it is an absolute waste of time if you question the OA or OE.




Remember that 30 minutes = 30*60=1800 seconds. 6 miles = 6*5280 = 31680 feet.

Per statement 1, you are given average speed > 16 ft/s ---> thus in 30 minutes, Carlos travels > 30*60*16 feet ---> > 28800 feet. Nw as the distance is > 28800 we can not be sure whether this value if 29000 or 32000, giving you 2 different answers ---> not sufficient.

Per statement 2, you are given average speed <18 ft/s ---> thus in 30 minutes, Carlos travels < 30*60*18 feet ---> < 32400 feet. Nw if the distance is 32399 feet, then "yes" but if the distance is 31600 feet, the answer is "no". Again, 2 different answers ---> not sufficient.

Combining the 2 statements, 28800 < distance < 32400 , again clearly if the distance is 31600 "no" but if it is 32000 "yes". Again not a unique answer.

E is thus the correct answer.

Hope this helps.
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 09 Jan 2016, 14:10
Hi pepo,

Training for the GMAT will always involve making some mistakes along the way - that's how you'll ultimately hone your GMAT skills and score at a higher level. As you continue to study, you'll find that much of the work that you have to do when answering GMAT questions isn't all that difficult, but it does involve many of the business 'skills' that MBA Programs want to make sure that you have: note-taking, organization, accuracy, attention-to-detail, precision/rounding (when either is asked for), etc.

You mentioned how your calculation proved that Fact 2 was sufficient, but you didn't actually show what your calculation was (or why it was ultimately incorrect). If you can go into a bit more detail about that work, then we should be able to help you make sure that the same mistake doesn't happen again.

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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 10 Jan 2016, 07:06
EMPOWERgmatRichC wrote:
Hi pepo,

Training for the GMAT will always involve making some mistakes along the way - that's how you'll ultimately hone your GMAT skills and score at a higher level. As you continue to study, you'll find that much of the work that you have to do when answering GMAT questions isn't all that difficult, but it does involve many of the business 'skills' that MBA Programs want to make sure that you have: note-taking, organization, accuracy, attention-to-detail, precision/rounding (when either is asked for), etc.

You mentioned how your calculation proved that Fact 2 was sufficient, but you didn't actually show what your calculation was (or why it was ultimately incorrect). If you can go into a bit more detail about that work, then we should be able to help you make sure that the same mistake doesn't happen again.

GMAT assassins aren't born, they're made,
Rich


Sure Rich! I will be happy to show you how I worked through the question:

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

For me is not sufficient because at this rate Carlos could have been cycled a distance less or greater than 6 miles.
Thas this fact is insufficient is quite evident, so I will focus no statement 2.

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

If the speed at which Carlos cycled was less than 18 feet per second, to check if the statement is sufficient, I can take in consideration a speed less than 18 feet/sec., for example 17 feet per second.
So, if Carlos cycled at 17 feet per second, it measn that his rate was also 1020 feet per minute and 30600 feet per 1/2 hour. Dividing 30600 by 5280 (1 mile = 5280 ft) I get 5,79 mile, which is not 6 mile. So, IMO Carlos didn't covered a distance greater or equal than 6 miles and the answer to the question is always NO.

Hope my line of reasoning was understandable, so you can quickly spot my mistake.

Thanks a lot :)
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 10 Jan 2016, 09:31
pepo wrote:
EMPOWERgmatRichC wrote:
Hi pepo,

Training for the GMAT will always involve making some mistakes along the way - that's how you'll ultimately hone your GMAT skills and score at a higher level. As you continue to study, you'll find that much of the work that you have to do when answering GMAT questions isn't all that difficult, but it does involve many of the business 'skills' that MBA Programs want to make sure that you have: note-taking, organization, accuracy, attention-to-detail, precision/rounding (when either is asked for), etc.

You mentioned how your calculation proved that Fact 2 was sufficient, but you didn't actually show what your calculation was (or why it was ultimately incorrect). If you can go into a bit more detail about that work, then we should be able to help you make sure that the same mistake doesn't happen again.

GMAT assassins aren't born, they're made,
Rich


Sure Rich! I will be happy to show you how I worked through the question:

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

For me is not sufficient because at this rate Carlos could have been cycled a distance less or greater than 6 miles.
Thas this fact is insufficient is quite evident, so I will focus no statement 2.

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

If the speed at which Carlos cycled was less than 18 feet per second, to check if the statement is sufficient, I can take in consideration a speed less than 18 feet/sec., for example 17 feet per second.
So, if Carlos cycled at 17 feet per second, it measn that his rate was also 1020 feet per minute and 30600 feet per 1/2 hour. Dividing 30600 by 5280 (1 mile = 5280 ft) I get 5,79 mile, which is not 6 mile. So, IMO Carlos didn't covered a distance greater or equal than 6 miles and the answer to the question is always NO.

Hope my line of reasoning was understandable, so you can quickly spot my mistake.

Thanks a lot :)


Couple of points to mention here. For saying statement 1 is not sufficient, you do not mention anything about the critical value of speed that will give you 31680 feet in 30 minutes. Without mentioning this value, how do you know whether 16 ft/s is sufficient ? What if 16 ft/s WAS the limiting value to give you 6 miles of distance travelled?

Coming back to your analysis of statement 2, when you have speed < 18 ft/s, you have infinite possible values to check and nowhere in the question was it mentioned that the limiting speed is an integer value. So, assuming speed = 17 ONLY had no basis. The limiting value is actually 17.6 ft/s which is still <18 . This is where you made a mistake.

DS questions are specially tricky if you do not follow step by step procedure and should never assume things not given.


Hope this helps.
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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New post 10 Jan 2016, 10:04
Engr2012 wrote:
pepo wrote:
EMPOWERgmatRichC wrote:
Hi pepo,

Training for the GMAT will always involve making some mistakes along the way - that's how you'll ultimately hone your GMAT skills and score at a higher level. As you continue to study, you'll find that much of the work that you have to do when answering GMAT questions isn't all that difficult, but it does involve many of the business 'skills' that MBA Programs want to make sure that you have: note-taking, organization, accuracy, attention-to-detail, precision/rounding (when either is asked for), etc.

You mentioned how your calculation proved that Fact 2 was sufficient, but you didn't actually show what your calculation was (or why it was ultimately incorrect). If you can go into a bit more detail about that work, then we should be able to help you make sure that the same mistake doesn't happen again.

GMAT assassins aren't born, they're made,
Rich


Sure Rich! I will be happy to show you how I worked through the question:

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

For me is not sufficient because at this rate Carlos could have been cycled a distance less or greater than 6 miles.
Thas this fact is insufficient is quite evident, so I will focus no statement 2.

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

If the speed at which Carlos cycled was less than 18 feet per second, to check if the statement is sufficient, I can take in consideration a speed less than 18 feet/sec., for example 17 feet per second.
So, if Carlos cycled at 17 feet per second, it measn that his rate was also 1020 feet per minute and 30600 feet per 1/2 hour. Dividing 30600 by 5280 (1 mile = 5280 ft) I get 5,79 mile, which is not 6 mile. So, IMO Carlos didn't covered a distance greater or equal than 6 miles and the answer to the question is always NO.

Hope my line of reasoning was understandable, so you can quickly spot my mistake.

Thanks a lot :)


Couple of points to mention here. For saying statement 1 is not sufficient, you do not mention anything about the critical value of speed that will give you 31680 feet in 30 minutes. Without mentioning this value, how do you know whether 16 ft/s is sufficient ? What if 16 ft/s WAS the limiting value to give you 6 miles of distance travelled?

Coming back to your analysis of statement 2, when you have speed < 18 ft/s, you have infinite possible values to check and nowhere in the question was it mentioned that the limiting speed is an integer value. So, assuming speed = 17 ONLY had no basis. The limiting value is actually 17.6 ft/s which is still <18 . This is where you made a mistake.

DS questions are specially tricky if you do not follow step by step procedure and should never assume things not given.


Hope this helps.




Thanks a lot! now it is clear. :)

One more question: is this an hard question? I mean, is this question skippable or it counts?
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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Attached is a visual that should help.
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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest  [#permalink]

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Re: If it took Carlos 1/2 hour to cycle from his house to the library yest   [#permalink] 12 Jun 2019, 02:24

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