NEW HERE? LEARN MORE
closeclose
Last visit was: 28 Apr 2024, 11:16 It is currently 28 Apr 2024, 11:16
Decision Tracker
My Rewards
New posts
New comers' posts

Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A jet is flying 2400 miles from Hawaii to San Francisco. In

User avatar
schumacher
Intern
Intern
Joined: 12 Dec 2004
Posts: 23
Own Kudos [?]: 4 [0]
Given Kudos: 0
Send PM
A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 10:32
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Hide Show timer Statistics
A jet is flying 2400 miles from Hawaii to San Francisco. In still
air, it flies at 600 mph. There is a 40 mph tailwind. How many hours
after takeoff would it be faster to just go to San Francisco than to
return to Hawaii in the case of an emergency?



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
avatar
semaphore
Intern
Intern
Joined: 05 Jan 2005
Posts: 1
Own Kudos [?]: [0]
Given Kudos: 0
Location: London
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 11:02
schumacher wrote:
A jet is flying 2400 miles from Hawaii to San Francisco. In still
air, it flies at 600 mph. There is a 40 mph tailwind. How many hours
after takeoff would it be faster to just go to San Francisco than to
return to Hawaii in the case of an emergency?


hi here is the solution.
Bcos of 40 mph tailwind avg speed is 600 + 40 = 640 mph.

2400/640 = 3.75 hrs

so if plane has travelled more that half then it makes sense to go to san francisco ..that hawii.....

so ...3.75/2 = 1.875 hrs is the answer !!!!!!!!!!!!!

Thanks :-D
Prince
User avatar
jinino
Manager
Manager
Joined: 31 Aug 2004
Posts: 61
Own Kudos [?]: 30 [0]
Given Kudos: 0
Location: Vancouver, BC, Canada
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 11:36
semaphore,

When the plane returns, the speed decreases to 540mph only. How can we incorporate this piece of information into the question?

According to your answer, the speed of plane to SF from H is the same as the speed from H to SF. :stupid
User avatar
banerjeea_98
Director
Director
Joined: 18 Nov 2004
Posts: 679
Own Kudos [?]: 198 [0]
Given Kudos: 0
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 11:52
I am getting 2.1 hrs.

I however took the speed as (600 - 40 = 560).

What's the OA ?
User avatar
maaverick
Manager
Manager
Joined: 19 Nov 2004
Posts: 144
Own Kudos [?]: 138 [0]
Given Kudos: 0
Location: Germany
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 14:00
2 Hours

Speed = distance / time

time = distance / speed

relative velocity from SF -> Hawaii = 640 kmph
relative velocity from Hawaii -> SF = 560 kmph

Consider that the jet is x km from Hawaii when it has to return

at this point in time, the jet is 2400 - x km from SF

Equating the time:

(2400 - x) / 640 = x / 560

Solving for x, we get x = 1120 which implies, the jet is 1280 from SF. At 640 kmph, it would take the jet 2 hours to cover this distance.
User avatar
toddmartin
Intern
Intern
Joined: 29 Jul 2004
Posts: 37
Own Kudos [?]: 1 [0]
Given Kudos: 0
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 14:34
maaverick wrote:
2 Hours

Speed = distance / time

time = distance / speed

relative velocity from SF -> Hawaii = 640 kmph
relative velocity from Hawaii -> SF = 560 kmph

Consider that the jet is x km from Hawaii when it has to return

at this point in time, the jet is 2400 - x km from SF

Equating the time:

(2400 - x) / 640 = x / 560

Solving for x, we get x = 1120 which implies, the jet is 1280 from SF. At 640 kmph, it would take the jet 2 hours to cover this distance.


Exactly the same approach I used. The only difference was I used the 1120 as the distance already traveled and reasoned if you had to fly back you'd go at 560. So the time would be D/R=1120/560=28/14=2 hours. The same basic idea but this way saves subtracting 1120 from 2400.
User avatar
schumacher
Intern
Intern
Joined: 12 Dec 2004
Posts: 23
Own Kudos [?]: 4 [0]
Given Kudos: 0
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   05 Jan 2005, 15:03
Quote:
2 Hours

Speed = distance / time

time = distance / speed

relative velocity from SF -> Hawaii = 640 kmph
relative velocity from Hawaii -> SF = 560 kmph

Consider that the jet is x km from Hawaii when it has to return

at this point in time, the jet is 2400 - x km from SF

Equating the time:

(2400 - x) / 640 = x / 560

Solving for x, we get x = 1120 which implies, the jet is 1280 from SF. At 640 kmph, it would take the jet 2 hours to cover this distance.



You are almost right. The question asks for the time already traveled, not the time that would take to complete the journey (either to Hawaii or to San Francisco)!!

Imagine that the plane had travelled t hours from Hawaii. It would have covered 640t miles (you are trying to determine at this point whether to go back or continue with the journey). Remaining distance to cover is 2400-640t miles. If you were to proceed, time it would take would be (2400-640t)/640. If you were to go back, the time that would take is 640t/560

Solving for t, we get 1.75 hours. This is the time from the take off.
User avatar
jinino
Manager
Manager
Joined: 31 Aug 2004
Posts: 61
Own Kudos [?]: 30 [0]
Given Kudos: 0
Location: Vancouver, BC, Canada
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   Updated on: 06 Jan 2005, 14:02
I agree with maaverick's answer. His wording in the last sentence is a bit confusing, but I think his point is if the plane leaves Hawaii 2 hours, it would be faster for the pilot to fly directly to SF than returning to Hawaii.
He does not mean the remaining time to reach SF when the plane is in the air is 2 hours.

Very nice approach from Maaverick. Correct me if I misinterpret your solution, Mavverick.

Originally posted by jinino on 06 Jan 2005, 10:27.
Last edited by jinino on 06 Jan 2005, 14:02, edited 2 times in total.
User avatar
banerjeea_98
Director
Director
Joined: 18 Nov 2004
Posts: 679
Own Kudos [?]: 198 [0]
Given Kudos: 0
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   06 Jan 2005, 13:47
Can someone please explain to me what exactly tailwind means, I am unsure on how r we saying that:

relative velocity from SF -> Hawaii = 640 kmph
relative velocity from Hawaii -> SF = 560 kmph
User avatar
jinino
Manager
Manager
Joined: 31 Aug 2004
Posts: 61
Own Kudos [?]: 30 [0]
Given Kudos: 0
Location: Vancouver, BC, Canada
Send PM
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink] New post   06 Jan 2005, 14:01
Tailwind here means the wind blows with the same direction when the plan travels from Hawaii to SF. It will make the plane faster in the direction from Hawaii to SF, but slower in the other way around.
This is my interpretation, and pls correct me if I am wrong.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: A jet is flying 2400 miles from Hawaii to San Francisco. In [#permalink]
06 Jan 2005, 14:01
Moderators:
Bunuel
Math Expert
92975 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions