How long did it take a certain airplane to fly from a remote airstrip to Nairobi, Kenya?
1.If a constant tailwind had increased the airplane's average speed by 20 percent, the trip would have taken 90 minutes.
2.The average speed of the airplane for the trip was 490 miles per hour.
Airplane (Knewton Prep)
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 132
- Joined: Thu Dec 02, 2010 2:49 am
- Thanked: 5 times
- manpsingh87
- Master | Next Rank: 500 Posts
- Posts: 436
- Joined: Tue Feb 08, 2011 3:07 am
- Thanked: 72 times
- Followed by:6 members
1) let d be the distance between remote strip and nairobi; average speed be v and time be t;RadiumBall wrote:How long did it take a certain airplane to fly from a remote airstrip to Nairobi, Kenya?
1.If a constant tailwind had increased the airplane's average speed by 20 percent, the trip would have taken 90 minutes.
2.The average speed of the airplane for the trip was 490 miles per hour.
under normal conditions time taken would be d/v=t;
as average speed is increased by 20% therefore it becomes 1.2v; and time taken would have been 90;
d/1.2v=90; we know that d/v=t; t=1.2*90; t=108; hence 1 alone is sufficient to answer the question.
2) since we don't know the distance; we can't find the time taken by traveling at the average speed of 490; hence 2 alone is not sufficient to answer the question..!!!
Hence A
O Excellence... my search for you is on... you can be far.. but not beyond my reach!
-
- Master | Next Rank: 500 Posts
- Posts: 132
- Joined: Thu Dec 02, 2010 2:49 am
- Thanked: 5 times
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
No math is needed here.RadiumBall wrote:How long did it take a certain airplane to fly from a remote airstrip to Nairobi, Kenya?
1.If a constant tailwind had increased the airplane's average speed by 20 percent, the trip would have taken 90 minutes.
2.The average speed of the airplane for the trip was 490 miles per hour.
Statement 1: If a constant tailwind had increased the airplane's average speed by 20 percent, the trip would have taken 90 minutes.
If we know the time needed when the speed is increased by x%, we can determine the time needed at the actual speed.
Sufficient.
If this were a PS question and we needed to determine the time, we could plug in a number for the distance.
Let d = 540 miles.
Rate for 90 minutes = d/t = 540/90 = 6 miles per minute.
This rate is 20% greater than the actual rate.
Thus, the actual rate is 5 miles per minute.
Time at 5 miles per minute = d/r = 540/5 = 108 minutes.
Statement 2.The average speed of the airplane for the trip was 490 miles per hour.
Without knowing the distance, we can't determine the time.
Insufficient.
The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3