GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 25 May 2019, 02:25

### 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

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

# At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a

Author Message
TAGS:

### Hide Tags

Intern
Joined: 30 Jan 2014
Posts: 17
At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

11 Feb 2014, 06:15
14
00:00

Difficulty:

65% (hard)

Question Stats:

58% (02:39) correct 42% (03:20) wrong based on 127 sessions

### HideShow timer Statistics

At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground and is on a direct approach (i.e., flying in a direct line to the runway) towards The Airport, which is located exactly 8 miles due north of the plane’s current position. Flight 501 is scheduled to land at The Airport at 8:00 am, but, at 7:57 am, the control tower radios the plane and changes the landing location to an airport 15 miles directly due east of The Airport. Assuming a direct approach (and negligible time to shift direction), by how many miles per hour does the pilot have to increase her speed in order to arrive at the new location on time?

A. $$5\sqrt{13} - 10$$ miles/hr

B. 100 miles/hr

C. $$100\sqrt{13} - 200$$ miles/hr

D. 200 miles/hr

E. $$100\sqrt{13}$$ miles/hr

_________________
Please +1 KUDO if my post helps. Thank you.
Manager
Joined: 25 Oct 2013
Posts: 143
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

14 Feb 2014, 03:51
7
4
Temurkhon wrote:
what if like this:
R*T=D
8/3m/min*3min=8miles
5m/min*3min=15miles
5-8/3=7/3m/min or 140m/hour

Given the flight has an altitude of 6 miles and the airport is exactly 8 miles due north. The flight has to descend to the airport along the hypotenuse of a right angled triangle with legs 6 & 8 miles. hypotenuse = 10 miles. after that we can apply your approach => 3 mins per 10 miles => 60 mins is 60*10/3 = 200 mph. ---original speed.

Now since the flight got a new destination exactly 15 miles east of the current airport. we have 2nd right angled triangle with 8 & 15 as legs. hypotenuse is 17. Further, now the flight has to descend to the new airport along the hypotenuse of a third triangle with legs 6 miles(altitude of the plane) & 17 miles which is $$\sqrt{6^2+17^2} = 5\sqrt{13}$$

The plane has to descend $$5\sqrt{13}$$ miles in 3 mins. hence in 60 mins it has to have a new speed of $$60*\frac{5}{3}\sqrt{13}$$

$$= 20*5\sqrt{13}$$ --- new speed

Increase in speed is $$20*5\sqrt{13}-20*10$$

$$20(5\sqrt{13}-10)$$
_________________
Click on Kudos if you liked the post!

Practice makes Perfect.
##### General Discussion
Senior Manager
Status: busyness school student
Joined: 09 Sep 2013
Posts: 419
Location: United States
Schools: Tepper '16 (M)
GMAT 1: 730 Q52 V37
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

11 Feb 2014, 06:40
6
2
Assume Euclidean geometry. If the original airport is 8 miles due north, and the new airport is 15 miles due east of the original airport, then the new airport is 17 miles away. (17² = 8² + 15²)

Now the plane is 6 miles above ground, and the original airport is 8 miles away. Then the Euclidean distance from the plane to the original airport is 10 miles (10² = 6² + 8²). Because it would have taken 3 minutes to travel the 10 miles, We can say it would have taken 10/3 miles/min.

The new airport is 17 miles away and the plane is 6 miles above ground. So the distance the plane must now travel is 5√13 miles( [5√13]² = 17² + 6²). To do this in 3 minutes, the plane must travel at 5√13/3 miles/min.

The difference in speed is thus 5√13/3 - 10/3 miles/min. But we need to find the answer in miles/hour, so we need to multiply by 60 to get 60(5√13/3 - 10/3) miles/hour or 20(5√13 - 10) miles/hour.
_________________
Director
Joined: 23 Jan 2013
Posts: 549
Schools: Cambridge'16
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

14 Feb 2014, 01:08
what if like this:
R*T=D
8/3m/min*3min=8miles
5m/min*3min=15miles
5-8/3=7/3m/min or 140m/hour
Intern
Joined: 09 Sep 2017
Posts: 5
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

21 Nov 2017, 04:02
Temurkhon wrote:
what if like this:
R*T=D
8/3m/min*3min=8miles
5m/min*3min=15miles
5-8/3=7/3m/min or 140m/hour

If you get 140m/hr, thats good enough since 100 √ 13−200 miles/hr is approximately 140 miles an hour.

√ 13 = between 3 (3*3=9) and 4(4*4=16). take 3.5 for example.

you'd get 100*3.5 - 200

you get a difference of approximately 150 m/hr which is the closest to the answer you got.
Non-Human User
Joined: 09 Sep 2013
Posts: 11013
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a  [#permalink]

### Show Tags

05 Jan 2019, 13:17
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a   [#permalink] 05 Jan 2019, 13:17
Display posts from previous: Sort by

# At 7:57 am, Flight 501 is at an altitude of 6 miles above the ground a

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.