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

 It is currently 22 Oct 2018, 06:12

### 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

# The first flight out of Phoenix airport had a late departure

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Manager
Status: D-Day is on February 10th. and I am not stressed
Affiliations: American Management association, American Association of financial accountants
Joined: 12 Apr 2011
Posts: 180
Location: Kuwait
Schools: Columbia university
The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

12 Jan 2012, 07:51
1
00:00

Difficulty:

45% (medium)

Question Stats:

61% (01:24) correct 39% (01:30) wrong based on 112 sessions

### HideShow timer Statistics

The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 90%?

A. 6
B. 7
C. 9
D. 10
E. 11

I will see what is the quickest way to solve it then I will provide the explanation

_________________

Sky is the limit

VP
Status: Top MBA Admissions Consultant
Joined: 24 Jul 2011
Posts: 1489
GMAT 1: 780 Q51 V48
GRE 1: Q800 V740
Re: first flight out of phoenix  [#permalink]

### Show Tags

13 Jan 2012, 04:28
1/(3+x) <= 0.1
=> x => 7

Therefore (B)
_________________

GyanOne | Top MBA Rankings and MBA Admissions Blog

Top MBA Admissions Consulting | Top MiM Admissions Consulting

Premium MBA Essay Review|Best MBA Interview Preparation|Exclusive GMAT coaching

Get a FREE Detailed MBA Profile Evaluation | Call us now +91 98998 31738

Intern
Joined: 30 Nov 2011
Posts: 7
Re: first flight out of phoenix  [#permalink]

### Show Tags

Updated on: 07 Mar 2012, 06:38
1
My approach:

If the first (one) flight had a late departure, then 1 flight out of 1 flight had a late departure (100% of the flights so far). Then, the stem says that the next 3 flights departed on-time, meaning that 1 out of 4 flights had a late departure (25% of the flights so far). Therefore, following this logic, if we add another 6 on-time planes, we will know that 1 out of 10 flights had a late departure (thus 10% was late and 90% was on-time).

The question asks how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be HIGHER than 90%. As we have seen so far, if 6 subsequent planes were on-time, we would have a rate of EXACTLY 90% of late departure. Therefore, for the airport's on-time departure rate to be HIGHER than 90%, we need 7 subsequent planes to be on-time (1 out of 11 had a late departure or aprox. 9% of the flights -- the remaining 91% is the rate of on-time flights).

Ans: B

Originally posted by pedroca on 06 Mar 2012, 22:25.
Last edited by pedroca on 07 Mar 2012, 06:38, edited 1 time in total.
Math Expert
Joined: 02 Sep 2009
Posts: 50039
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

06 Mar 2012, 22:55
2
manalq8 wrote:
The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 90%?

A. 6
B. 7
C. 9
D. 10
E. 11

I will see what is the quickest way to solve it then I will provide the explanation

The following approach might be the easiest one and less error prone.

We need on-time departure rate to be higher than 9/10, so it should be at least 10/11, which means that 10 out of 11 flights must depart on time. Since for now 3 out of 4 flights departed on time then 10-3=7 subsequent flights need to depart on-time.

Answer: B.
_________________
Intern
Status: K... M. G...
Joined: 22 Oct 2012
Posts: 36
Concentration: General Management, Leadership
GMAT Date: 08-27-2013
GPA: 3.8
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

11 Feb 2013, 10:18
Bunuel wrote:
manalq8 wrote:
The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 90%?

A. 6
B. 7
C. 9
D. 10
E. 11

I will see what is the quickest way to solve it then I will provide the explanation

The following approach might be the easiest one and less error prone.

We need on-time departure rate to be higher than 9/10, so it should be at least 10/11, which means that 10 out of 11 flights must depart on time. Since for now 3 out of 4 flights departed on time then 10-3=7 subsequent flights need to depart on-time.

Answer: B.

one flight was already late & 3 flight were on time departure so now to have a on-time departure rate to be higher than 9/10,

3 on time + 6 yet to be on time = 9 on time. total of 10, 9 on time but it not higher than 9/10 so so we went for 7 by considering 10/11?
Math Expert
Joined: 02 Sep 2009
Posts: 50039
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

11 Feb 2013, 10:31
FTG wrote:
Bunuel wrote:
manalq8 wrote:
The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 90%?

A. 6
B. 7
C. 9
D. 10
E. 11

I will see what is the quickest way to solve it then I will provide the explanation

The following approach might be the easiest one and less error prone.

We need on-time departure rate to be higher than 9/10, so it should be at least 10/11, which means that 10 out of 11 flights must depart on time. Since for now 3 out of 4 flights departed on time then 10-3=7 subsequent flights need to depart on-time.

Answer: B.

one flight was already late & 3 flight were on time departure so now to have a on-time departure rate to be higher than 9/10,

3 on time + 6 yet to be on time = 9 on time. total of 10, 9 on time but it not higher than 9/10 so so we went for 7 by considering 10/11?

Yes, you can say so.
_________________
Manager
Joined: 13 Jul 2013
Posts: 66
GMAT 1: 570 Q46 V24
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

19 Sep 2013, 10:25
how did you calculate 10/11?
SVP
Joined: 06 Sep 2013
Posts: 1764
Concentration: Finance
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

26 Dec 2013, 10:46
manalq8 wrote:
The first flight out of Phoenix airport had a late departure. If the next three flights departed on-time, how many subsequent flights need to depart from Phoenix on-time, for the airport's on-time departure rate to be higher than 90%?

A. 6
B. 7
C. 9
D. 10
E. 11

I will see what is the quickest way to solve it then I will provide the explanation

3+x/4+x >9/10
x>6

Hence B is our best choice

Cheers!
J
Manager
Joined: 05 Nov 2012
Posts: 149
Re: The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

26 Dec 2013, 11:21
theGame001 wrote:
how did you calculate 10/11?

here is my approach to this question.
Let the total number of flights be 'x'. On time departure rate should be more than 90%.
it is said that 1 flight is late.... so out of x flights is 1 flight is late remaining (x-1) flights will be on-time...
so $$\frac{(x-1)}{x}*100=90$$
solving for x we get 10...... but remember we want on-time departure rate to be more than 90%, not exactly 90%..... so minimum number of flights to take off is 11.....
since first one is late and remaining 3 left so the next 7 flights should also be on-time..... So answer is 7...
Intern
Joined: 23 Jan 2018
Posts: 25
Location: United States
Concentration: Marketing, Nonprofit
GPA: 3.7
WE: Marketing (Advertising and PR)
The first flight out of Phoenix airport had a late departure  [#permalink]

### Show Tags

17 Mar 2018, 16:56
I agree with the short-cut proposed by bb. However, the method requires the sensibility in math, and I do not like it. The other easy way is to test each answer, and start with A, then B,...
I think the question asks about the minimum subsequent flights; otherwise, answer can be infinite.
The first flight out of Phoenix airport had a late departure &nbs [#permalink] 17 Mar 2018, 16:56
Display posts from previous: Sort by

# The first flight out of Phoenix airport had a late departure

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 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®.