Airplanes A and B traveled the same 360-mile route...

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

Airplanes A and B traveled the same 360-mile route...

by BTGmoderatorLU » Fri Nov 03, 2017 9:29 am

Airplanes A and B traveled the same 360-mile route. If airplane A took 2 hours and airplane B traveled at an average speed that was 1/3 slower than the average speed of airplane A, how many hours did it take airplane B to travel the route?

(A) 2

(B) 2(1/3)

(C) 2(1/2)

(D) 2(2/3)

(E) 3

The OA is E.

I don't understand why that is the correct answer. Please can any expert explain this PS question for me? Thanks.

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Source: Beat The GMAT — Problem Solving | Fri Nov 03, 2017 9:29 am

DavidG@VeritasPrep: Legendary Member; Posts: 2663; Joined: Wed Jan 14, 2015 8:25 am; Location: Boston, MA; Thanked: 1153 times; Followed by:128 members; GMAT Score:770

by DavidG@VeritasPrep » Fri Nov 03, 2017 9:53 am

LUANDATO wrote:Airplanes A and B traveled the same 360-mile route. If airplane A took 2 hours and airplane B traveled at an average speed that was 1/3 slower than the average speed of airplane A, how many hours did it take airplane B to travel the route?

(A) 2

(B) 2(1/3)

(C) 2(1/2)

(D) 2(2/3)

(E) 3

The OA is E.

I don't understand why that is the correct answer. Please can any expert explain this PS question for me? Thanks.

Time and rate have a reciprocal relationship. For example, if you run twice as fast I do, you'd cover the same distance in 1/2 the time. If you ran 4/3 as fast as I did, you'd cover the same distance in 3/4 the time, etc.

If plane B's rate is 1/3 less than A's rate, then B's rate is 2/3 of A's rate.
If B's rate is 2/3 of A's rate, then it covers the same distance in 3/2 the time. If A did the trip in 2 hours, then B did it in (3/2)*2 = 3 hours. The answer is E.

(Note that the actual distance doesn't matter here. What's relevant is that each plane traveled the same distance.)

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GMAT/MBA Expert

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by [email protected] » Sun Nov 05, 2017 12:24 pm

Hi LUANDATO,

David's explanation about the relationship between Rate and Time is spot-on. If you don't realize how that relationship applies in these types of questions, then you can still answer this question with some basic arithmetic.

We're told that Airplane A traveled a 360-mile route in 2 hours. Thus, it traveled at 360/2 = 180 miles per hour.

We're also told that Airplane B traveled the SAME distance at an average speed that was 1/3 SLOWER than the average speed of airplane A. One third of 180 is 60, so Airplane B traveled at 180 - 60 = 120 miles per hour.

We're asked for the number of hours that it took Airplane B to travel the route....
Distance = (Rate)(Time)
360 miles = (120 mi/hour)(T)
360/120 = T
3 hours = T

Final Answer: E

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Rich

Contact Rich at [email protected]

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by Scott@TargetTestPrep » Sun Nov 03, 2019 7:37 pm

BTGmoderatorLU wrote:Airplanes A and B traveled the same 360-mile route. If airplane A took 2 hours and airplane B traveled at an average speed that was 1/3 slower than the average speed of airplane A, how many hours did it take airplane B to travel the route?

(A) 2

(B) 2(1/3)

(C) 2(1/2)

(D) 2(2/3)

(E) 3

The OA is E.

I don't understand why that is the correct answer. Please can any expert explain this PS question for me? Thanks.

We find that airplane A traveled at an average speed of 360/2 = 180 mph.

Since airplane B traveled at an average speed that was 180 * (1/3) = 60 mph less than that of airplane A, the speed of airplane B is 180 - 60 = 120 mph.

Thus, it took airplane B 360/120 = 3 hours to travel the route.

Answer: E

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