GMAT Prep
How many hours did it take Helen to drive from her house to her parent's house?
1) Helen's average speed on this trip was 72 kilometers per hour.
2) If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.
OA C
How many hours did it take Helen to drive from her house to
This topic has expert replies
GMAT/MBA Expert
- Jay@ManhattanReview
- GMAT Instructor
- Posts: 3008
- Joined: Mon Aug 22, 2016 6:19 am
- Location: Grand Central / New York
- Thanked: 470 times
- Followed by:34 members
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
Say the distance from Helen's home to her parent's house is d kilometers.AAPL wrote:GMAT Prep
How many hours did it take Helen to drive from her house to her parent's house?
1) Helen's average speed on this trip was 72 kilometers per hour.
2) If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.
OA C
We have to get the value of d.
Let's take each statement one by one.
1) Helen's average speed on this trip was 72 kilometers per hour.
=> time taken by Helen = d/72 hours.
Can't get the value of d. insufficient.
2) If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.
Only this information can't information. Insufficient.
(1) and (2) together
=> d/72 - d/80 = 1
Since this is a linear relationship, we will get a unique value of d. Sufficient.
Since this is a DS question, we need not get the actual value.
The correct answer: C
Hope this helps!
-Jay
_________________
Manhattan Review
Locations: Manhattan Review Jayanagar | GMAT Prep Tarnaka | GRE Prep Madhapur | Kukatpally GRE Coaching | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
-
- Newbie | Next Rank: 10 Posts
- Posts: 2
- Joined: Fri May 06, 2022 2:40 am
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
d=rtd=rt , where dd is the distance covered, rr rate and tt time. Question: t=?t=?
(1) r=72r=72. Clearly not sufficient.
(2) (r+8)(t−1)=d(r+8)(t−1)=d. Clearly not sufficient.
(1)+(2) r=72r=72 and (r+8)(t−1)=d(r+8)(t−1)=d --> 80(t−1)=d80(t−1)=d --> d=80(t−1)=rt=72td=80(t−1)=rt=72t --> 8t=808t=80 --> t=10t=10. Sufficient.
Answer is C
(1) r=72r=72. Clearly not sufficient.
(2) (r+8)(t−1)=d(r+8)(t−1)=d. Clearly not sufficient.
(1)+(2) r=72r=72 and (r+8)(t−1)=d(r+8)(t−1)=d --> 80(t−1)=d80(t−1)=d --> d=80(t−1)=rt=72td=80(t−1)=rt=72t --> 8t=808t=80 --> t=10t=10. Sufficient.
Answer is C