From Aqua-Bella island, it is possible to reach Aqua-Marine island by either ferry A or ferry B. Ferry A sails 3 hours at 7 kilometers per hour, while ferry B takes a route that is three times longer. If ferry A is slower than ferry B by 2 kilometers per hour, How many hours longer is the journey of ferry B compared with the journey of ferry A?
A. 4
B. 7
C. 8.6
D. 9.6
E. 12.6
The OA is A.
I solved this PS question as follow,
I drew two diagrams:
3 hrs. 7 km/hr
A:-------------->
21 km
7 hrs. 9 km/hr
B:-------------->
63 km
7-3 = 4, answer A.
We have a lot of given information. 3 hrs at 7 km/h for A. This makes a total of 21 km. If B is 3x longer, then the trip for B is 63 km. If A's ferry is 2 km/h shorter, then B's speed is 9. 63/9 gives us 7 hrs for the trip.
Is there a strategic approach to this question? Can any experts help?
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
From Aqua-Bella island, it is possible to reach Aqua-Marine.
This topic has expert replies
GMAT/MBA Expert
-
ErikaPrepScholar
- Legendary Member
- Posts: 503
- Joined: Thu Jul 20, 2017 9:03 am
- Thanked: 86 times
- Followed by:15 members
- GMAT Score:770
First thing: the OA for this problem should be A, 4 hours. This means that you solved this question correctly!
You could also do the same math using dimensional analysis for potentially quicker and cleaner work:
$$3\ hours\ A\ \left(\frac{7\ km\ A}{1\ hour\ A}\right)\left(\frac{3\ km\ B}{1\ km\ A}\right)\left(\frac{1\ hour\ B}{9\ km\ B}\right)=7\ hours\ B$$
You could also do the same math using dimensional analysis for potentially quicker and cleaner work:
$$3\ hours\ A\ \left(\frac{7\ km\ A}{1\ hour\ A}\right)\left(\frac{3\ km\ B}{1\ km\ A}\right)\left(\frac{1\ hour\ B}{9\ km\ B}\right)=7\ hours\ B$$
Erika John - Content Manager/Lead Instructor
https://gmat.prepscholar.com/gmat/s/
Get tutoring from me or another PrepScholar GMAT expert: https://gmat.prepscholar.com/gmat/s/tutoring/
Learn about our exclusive savings for BTG members (up to 25% off) and our 5 day free trial
Check out our PrepScholar GMAT YouTube channel, and read our expert guides on the PrepScholar GMAT blog
GMAT/MBA Expert
-
Jeff@TargetTestPrep
- GMAT Instructor
- Posts: 1462
- Joined: Thu Apr 09, 2015 9:34 am
- Location: New York, NY
- Thanked: 39 times
- Followed by:22 members
Since distance = rate x time, we see that ferry A's route is 7 x 3 = 21 km long. Since ferry B's route is three times longer, ferry B's route is 21 x 3 = 63 km long. Since ferry B is 2 km/hr faster, ferry B's rate is 9 km/hr. Thus, ferry B's time = 63/9 = 7 hours, and that is 4 hours longer than ferry A's time.AAPL wrote:From Aqua-Bella island, it is possible to reach Aqua-Marine island by either ferry A or ferry B. Ferry A sails 3 hours at 7 kilometers per hour, while ferry B takes a route that is three times longer. If ferry A is slower than ferry B by 2 kilometers per hour, How many hours longer is the journey of ferry B compared with the journey of ferry A?
A. 4
B. 7
C. 8.6
D. 9.6
E. 12.6
Answer: A
Jeffrey Miller
Head of GMAT Instruction
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews
