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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

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

Show Tags

12 Jan 2012, 06:51

2

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

55% (hard)

Question Stats:

56% (01:42) correct
44% (00:39) wrong based on 62 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

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

Last edited by pedroca on 07 Mar 2012, 05:38, edited 1 time in total.

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.

Re: The first flight out of Phoenix airport had a late departure [#permalink]

Show Tags

11 Feb 2013, 09:18

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?

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?

Re: The first flight out of Phoenix airport had a late departure [#permalink]

Show Tags

26 Dec 2013, 09:46

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

Re: The first flight out of Phoenix airport had a late departure [#permalink]

Show Tags

26 Dec 2013, 10:21

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...

gmatclubot

Re: The first flight out of Phoenix airport had a late departure
[#permalink]
26 Dec 2013, 10:21

Happy New Year everyone! Before I get started on this post, and well, restarted on this blog in general, I wanted to mention something. For the past several months...

It’s quickly approaching two years since I last wrote anything on this blog. A lot has happened since then. When I last posted, I had just gotten back from...

Happy 2017! Here is another update, 7 months later. With this pace I might add only one more post before the end of the GSB! However, I promised that...

The words of John O’Donohue ring in my head every time I reflect on the transformative, euphoric, life-changing, demanding, emotional, and great year that 2016 was! The fourth to...