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Hogwarts Express covers the distance between King’s Cross station and

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Hogwarts Express covers the distance between King’s Cross station and  [#permalink]

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New post 27 Feb 2019, 03:08
1
2
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A
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C
D
E

Difficulty:

  35% (medium)

Question Stats:

71% (01:38) correct 29% (01:39) wrong based on 135 sessions

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Hogwarts Express covers the distance between King’s Cross station and Hogsmeade station. On a certain day, the train travelled through a different track to reach the Hogsmeade from King's Cross. Was the train late by more than an hour of the scheduled time?

    Statement 1. The average speed of Hogwarts Express on that trip was within 15 miles per hour of the regular average speed.
    Statement 2. The distance travelled on that day was within 30 miles of the original distance.


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Re: Hogwarts Express covers the distance between King’s Cross station and  [#permalink]

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New post 01 Mar 2019, 02:54

Solution



Given:
In this question, we are given that
    • Hogwarts Express covers the distance between King’s Cross station and Hogsmeade station.
    • On a certain day, the train travelled through a different track to reach the Hogsmeade.

To find:
We need to determine
    • On that certain day, whether the train was late by more than an hour of the scheduled time or not.

Analysing Statement 1
As per the information given in statement 1, the average speed of Hogwarts Express on that trip was within 15 miles per hour of the regular average speed.
    • If the average speed of the train on a regular day was S, then on that day the average speed was in the range: S – 15 ≤ average speed on that day ≤ S + 15
    • However, we don’t have any specific information either about the average speed value or the distance covered.

Hence, statement 1 is not sufficient to answer the question.

Analysing Statement 2
As per the information given in statement 2, the distance travelled on that day was within 30 miles of the original distance.
    • If the distance travelled on a regular day was D, then on that day the distance travelled was in the range: D – 30 ≤ distance travelled on that day ≤ D + 30
    • However, we don’t have any specific information either about the specific value of the distance travelled or the speed at which the distance was covered.

Hence, statement 2 is not sufficient to answer the question.

Combining Both Statements
If we combine both statements, we get
    • S – 15 ≤ average speed on that day ≤ S + 15
    • D – 30 ≤ distance travelled on that day ≤ D + 30

However, we still cannot find the exact values of average speed or the distance travelled.

Hence, the correct answer is option E.

Answer: E
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Re: Hogwarts Express covers the distance between King’s Cross station and  [#permalink]

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New post 29 Apr 2019, 11:52
EgmatQuantExpert wrote:

Solution



Given:
In this question, we are given that
    • Hogwarts Express covers the distance between King’s Cross station and Hogsmeade station.
    • On a certain day, the train travelled through a different track to reach the Hogsmeade.

To find:
We need to determine
    • On that certain day, whether the train was late by more than an hour of the scheduled time or not.

Analysing Statement 1
As per the information given in statement 1, the average speed of Hogwarts Express on that trip was within 15 miles per hour of the regular average speed.
    • If the average speed of the train on a regular day was S, then on that day the average speed was in the range: S – 15 ≤ average speed on that day ≤ S + 15
    • However, we don’t have any specific information either about the average speed value or the distance covered.

Hence, statement 1 is not sufficient to answer the question.

Analysing Statement 2
As per the information given in statement 2, the distance travelled on that day was within 30 miles of the original distance.
    • If the distance travelled on a regular day was D, then on that day the distance travelled was in the range: D – 30 ≤ distance travelled on that day ≤ D + 30
    • However, we don’t have any specific information either about the specific value of the distance travelled or the speed at which the distance was covered.

Hence, statement 2 is not sufficient to answer the question.

Combining Both Statements
If we combine both statements, we get
    • S – 15 ≤ average speed on that day ≤ S + 15
    • D – 30 ≤ distance travelled on that day ≤ D + 30

However, we still cannot find the exact values of average speed or the distance travelled.

Hence, the correct answer is option E.

Answer: E


if you take i.e.
d=45 & s=20 ----------> t= 2.25h

now apply the + deviation:
d = 15 & s=5 ----------> t= 3h

therefore, the guy could not deviate more than 1h from the 2.25h , so the guy CAN'T arrive more than 1h late, thus c).

What am I doing wrong?
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Re: Hogwarts Express covers the distance between King’s Cross station and  [#permalink]

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New post 30 Apr 2019, 18:57
1
Hey alpacino,
You are solivng the question by taking some numbers and solving only for those, that is why you are getting the wrong answer.

Also, you are taking only one case.
What if when D = 45-30 =15 then S = 20 +15 =35?
This is also a possible case.

Once you find the value of T, you will find the mistake.

Tip: Do not solve a DS question by assuming random numbers. At times, you will get the wrong answer.

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Re: Hogwarts Express covers the distance between King’s Cross station and  [#permalink]

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New post 10 Jun 2019, 08:59
EgmatQuantExpert wrote:

Solution



Given:
In this question, we are given that
    • Hogwarts Express covers the distance between King’s Cross station and Hogsmeade station.
    • On a certain day, the train travelled through a different track to reach the Hogsmeade.

To find:
We need to determine
    • On that certain day, whether the train was late by more than an hour of the scheduled time or not.

Analysing Statement 1
As per the information given in statement 1, the average speed of Hogwarts Express on that trip was within 15 miles per hour of the regular average speed.
    • If the average speed of the train on a regular day was S, then on that day the average speed was in the range: S – 15 ≤ average speed on that day ≤ S + 15
    • However, we don’t have any specific information either about the average speed value or the distance covered.

Hence, statement 1 is not sufficient to answer the question.

Analysing Statement 2
As per the information given in statement 2, the distance travelled on that day was within 30 miles of the original distance.
    • If the distance travelled on a regular day was D, then on that day the distance travelled was in the range: D – 30 ≤ distance travelled on that day ≤ D + 30
    • However, we don’t have any specific information either about the specific value of the distance travelled or the speed at which the distance was covered.

Hence, statement 2 is not sufficient to answer the question.

Combining Both Statements
If we combine both statements, we get
    • S – 15 ≤ average speed on that day ≤ S + 15
    • D – 30 ≤ distance travelled on that day ≤ D + 30

However, we still cannot find the exact values of average speed or the distance travelled.

Hence, the correct answer is option E.

Answer: E


Thought "within 30 miles" means "<=30 miles" so I picked C. Turned out "within" means "more or less".
Is that always the case in GMAT?
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Re: Hogwarts Express covers the distance between King’s Cross station and   [#permalink] 10 Jun 2019, 08:59
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