Sheldon left his house at 8:30 a.m. and drove to his friend's house

Question

Sheldon left his house at 8:30 a.m. and drove to his friend's house, arriving later that morning at 11:30 a.m. How many kilometers did he drive?

(1) He stopped twice along the way.

(2) His average speed while he was driving was 96 kilometers per hour.

gmatophobia · Accepted Answer

Statement 1

(1) He stopped twice along the way.

The statement alone is not sufficient as we don't have any information on how much time Sheldon drove. The statement alone is not sufficient and we can eliminate A and D.

Statement 2

(2) His average speed while he was driving was 96 kilometers per hour.

While we know the average speed at which Sheldon was driving, we don't know any information on the actual time he drove.

Note: We can not take the time as 2 hours, because Statement 2 mentions that

His average speed  while he was driving  was 96 kilometers per hour.

This statement alone is not sufficient to find the distance. We can eliminate B

Combined

From statement 1, we know that Sheldon stopped twice, however as the total duration of his stops is not known we cannot find the driving time. Without that information, we will not be able to find the distance.

Hence, the statements combined do not help.

Option E

gmatophobia · Answer

lunars  - Thank you for sharing your thoughts. I may not completely agree with the highlighted parts, but here is my take on your question.

I assume you're inclined to state that Statement 2 is sufficient as the average speed is given. If that's the case, I would have agreed with your assumption if Statement 2 were framed as "His average speed  while he was driving  was 96 kilometers per hour."

However, statement 2 tells us "His average speed  while he was driving  was 96 kilometers per hour". The portion in bold is what changes our approach to this question. The statement states that while he was driving (not throughout) the average speed was 96 kmph, thereby giving room for the possibility that Sheldon was probably not driving all along. Note, that I am still using the word 'possibility'.

Do we have complete (100%) information to state that Statement 2 is sufficient - No! We may be 99% sure that Sheldon drove for the entire period without stopping or doing anything else, but there is a 1% chance, based on the verbiage, that Sheldon might not have driven for the entire time. Hence, statement 2 is not sufficient.

Also, the makers of the question were generous enough to provide some details/hints in Statement 1. ( Yes! I agree, that one shouldn't refer to the other statement - all I am saying is the question provides us enough hints and information to doubt the highlighted assumption that Sheldon drove for the entire period without stopping).

Eliminating unwarranted assumptions and precise reading play a crucial role in this question.

Hope this helps!

rakman123 · Answer

gmatophobia  doesn’t the stem say he drove for 3 hours? From 8:30 to 11:30? Meaning 3hours x avg speed of 96km could give us the total distance?

Appreciate the help

gmatophobia · Answer

rakman123  - I am afraid that we cannot infer that Sheldon drove for 3 hours.

The question premise states that -

Sheldon left his house at 8:30 a.m . and  drove to his friend's house ,  arriving later that morning at 11:30 a.m . How many kilometers did he drive?

What we know?

Sheldon left his house at 8:30 am 
 Sheldon arrived at his friend's house at 11:30 am 
 Sheldon drove to his friend's house (he didn't walk, crawl, run, etc. )

While it's possible that the actual driving time was the entire 3 hours (i.e. from 8:30 am to 11:30 am), it's also possible that the actual driving time was only a part of the 3 hours.

For example, Sheldon drove from 8:30 am to 9:30 am, stopped for breakfast at the Cheese Cake Factory, had breakfast from 9:30 am to 10:00 am, and then drove from 10:00 am to 11:30 am. Therefore, Sheldon drove only for 2.5 hours.

Hope this helps !

lunars · Answer

gmatophobia  I think in the Data Sufficiency questions we are not supposed to interpret the stem, but we should assume that if it mentions that he drove, he drove for the entire period without stopping or doing anything else. If we are questioning and interpreting the stem, it becomes very very hard to answer the mathematical questions.

lunars · Answer

gmatophobia  thanks for expressing your thoughts. I still think that it’s very stretched and not consistent across all the Data Sufficiency questions. According to your interpretation the answer to this    would be E, while instead is B.

This because the question assumes that Chloe was only driving, and getting back home it took 1 hour more. We don’t know if Chloe stopped for 30 minutes for gasoline or to buy candy (and also in that question the first answer choice suggests that Chloe could stop)

Posted from my mobile device

gmatophobia · Answer

As I stated in my earlier response, the verbiage plays an important role in the context of this question. Hence, you might need to refer to the quoted question, which in fact is not an official question, to determine whether you can assume that stoppage times are taken into account.

P.S. - As the quoted question is not an official question, I don't suppose the question is a very good example to refer to and debate on.

JeffTargetTestPrep · Answer

We know that the total time = 3 hours, and we need to answer the question: total distance = ? Statement One Alone: => He stopped twice along the way. Since he stopped twice, he spent less than 3 hours driving. Without any information related to his speed, we can’t answer the question. Statement one is not sufficient. Eliminate answer choices A and D. Statement Two Alone: => His average speed while he was driving was 96 kilometers per hour. “While he was driving” is a clue that he might not have been driving continuously during his journey. If driving time ≠ journey time, then average driving speed ≠ average journey speed. Although we know that journey time = 3 hours and average driving speed = 96 kmph, we still can’t determine the total distance, which would be equal to either (average journey speed)(journey time) or (average driving speed)(driving time). Statement two is not sufficient. Eliminate answer choice B. Statements One and Two Together: Since driving time < 3 hours, we have: (average driving speed)(driving time) < (96 kmph)(3 hours) total distance < 288 km Without more information, we can’t answer the question. The two statements together are not sufficient. Answer: E

tomloveless · Answer

This is on a mock. OA for sure. Sadly we have to infer that he could be taking bathroom breaks which is an unfortunate complexity.

habenae · Answer

What if the question was:

In average, how many KM did he drive? Then would we be able to use statement (2) to resolve?

Since the question is: How many (exactly) kM did he drive and we are given an avg speed, this is not sufficient.

please help.

Bunuel · Answer

The answer to the original question is E because we don’t know how many hours Sheldon was actually driving. If we had that information, we could multiply the driving time by 96 to determine the total distance covered.

However, your reworded question doesn’t make sense. What does "how many kilometers on average did he drive" even mean?

Chibvike · Answer

Thanks a lot for your explanation.

Is it also fair to say that Statement 1: "  He stopped twice along the way"  gave us an indication that drive time does not equal journey time because we are not able to determine how long the stop lasted for.

ablatt4 · Answer

The prompt gives us insight that Sheldon drove for 3 hours. We have the time now we need the rate or distance.

1- this tells us nothing about rate or distance  insufficient

2- this tells us his average speed  while driving  but we don't know his average speed during the trips  insufficient

If we take the info from both and combine we know the speed he went while driving and that he stopped twice however the stops could have been 10 total seconds and could have been 2 hours, we are not given enough info to determine 
 E

Sheldon left his house at 8:30 a.m. and drove to his friend's house

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GMAT Data Sufficiency (DS) Questions

Sheldon left his house at 8:30 a.m. and drove to his friend's house

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