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

It is currently 19 Jun 2018, 09:13

LIVE NOW:

Tips for Your Best Possible Application - Live Chat with Tuck Admissions | Click Here to JOIN!


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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

The average (arithmetic mean) length per film for a group of 21 films

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

Hide Tags

5 KUDOS received
Director
Director
User avatar
G
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 645
Location: United States (CA)
Age: 38
GMAT 1: 770 Q47 V48
GMAT 2: 730 Q44 V47
GMAT 3: 750 Q50 V42
GRE 1: 337 Q168 V169
WE: Education (Education)
The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 05 May 2016, 19:27
5
4
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

77% (01:20) correct 23% (01:24) wrong based on 326 sessions

HideShow timer Statistics

The average (arithmetic mean) length per film for a group of 21 films is t minutes. If a film that runs for 66 minutes is removed from the group and replaced by one that runs for 52 minutes, what is the average length per film, in minutes, for the new group of films, in terms of t?

A) \(t + \frac{2}{3}\)

B) \(t - \frac{2}{3}\)

C) \(21t+14\)

D) \(t + \frac{3}{2}\)

E) \(t - \frac{3}{2}\)

Attachments

Screen Shot 2016-05-05 at 7.04.23 PM.png
Screen Shot 2016-05-05 at 7.04.23 PM.png [ 107.79 KiB | Viewed 4360 times ]


_________________

Harvard grad and 99% GMAT scorer, offering expert, private GMAT tutoring and coaching, both in-person (San Diego, CA, USA) and online worldwide, since 2002.

One of the only known humans to have taken the GMAT 5 times and scored in the 700s every time (700, 710, 730, 750, 770), including verified section scores of Q50 / V47, as well as personal bests of 8/8 IR (2 times), 6/6 AWA (4 times), 50/51Q and 48/51V (1 question wrong).

You can download my official test-taker score report (all scores within the last 5 years) directly from the Pearson Vue website: https://tinyurl.com/y8zh6qby Date of Birth: 09 December 1979.

GMAT Action Plan and Free E-Book - McElroy Tutoring

1 KUDOS received
Director
Director
User avatar
G
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 645
Location: United States (CA)
Age: 38
GMAT 1: 770 Q47 V48
GMAT 2: 730 Q44 V47
GMAT 3: 750 Q50 V42
GRE 1: 337 Q168 V169
WE: Education (Education)
The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post Updated on: 06 May 2016, 12:30
1
Logic tells us that the average length per film will go down, so we can eliminate all answers that add to the original average of t. That leaves either B or E. When executing the algebra, the key step is being able to quickly and easily turn one fraction with two numerators \((\frac{21t-14}{21})\) into two fractions with one numerator each \((\frac{21t}{21}-\frac{14}{21})\).

Above is a visual that should help.
_________________

Harvard grad and 99% GMAT scorer, offering expert, private GMAT tutoring and coaching, both in-person (San Diego, CA, USA) and online worldwide, since 2002.

One of the only known humans to have taken the GMAT 5 times and scored in the 700s every time (700, 710, 730, 750, 770), including verified section scores of Q50 / V47, as well as personal bests of 8/8 IR (2 times), 6/6 AWA (4 times), 50/51Q and 48/51V (1 question wrong).

You can download my official test-taker score report (all scores within the last 5 years) directly from the Pearson Vue website: https://tinyurl.com/y8zh6qby Date of Birth: 09 December 1979.

GMAT Action Plan and Free E-Book - McElroy Tutoring


Originally posted by mcelroytutoring on 05 May 2016, 19:28.
Last edited by mcelroytutoring on 06 May 2016, 12:30, edited 6 times in total.
Expert Post
3 KUDOS received
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 5890
Re: The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 05 May 2016, 20:09
3
mcelroytutoring wrote:
The average (arithmetic mean) length per film for a group of 21 films is t minutes. If a film that runs for 66 minutes is removed from the group and replaced by one that runs for 52 minutes, what is the average length per film, in minutes, for the new group of films, in terms of t?

A) \(t + \frac{2}{3}\)

B) \(t - \frac{2}{3}\)

C) \(21t+14\)

D) \(t + \frac{3}{2}\)

E) \(t - \frac{3}{2}\)


hi,
you do not have to get into any calculations if you understand and take the Q logically..

avg time for 21 is t min..
you add 52 and remove 66.. so basically you are removing 14 min from total..
effect on each or average =\(\frac{14}{21}= \frac{2}{3}\)..

so final average = \(t-\frac{2}{3}\)...
B
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html


GMAT online Tutor

2 KUDOS received
BSchool Forum Moderator
User avatar
D
Joined: 12 Aug 2015
Posts: 2642
GRE 1: 323 Q169 V154
GMAT ToolKit User Premium Member
Re: The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 15 Dec 2016, 14:05
2
Wharton Thread Master
avatar
B
Joined: 30 May 2015
Posts: 40
GMAT ToolKit User Premium Member Reviews Badge
Re: The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 20 Jul 2017, 15:08
average = sum of numbers/total number
t = s/21
s = 21t
Now as per question
s =21t -66 +52
s = 21t - 14
New average
t1 = (21t - 14) / 21
=> t - 2/3
Director
Director
User avatar
G
Joined: 09 Mar 2016
Posts: 600
The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 06 Mar 2018, 09:16
stonecold wrote:
Great Solutions above.
Here is my solution =>
Average length = t minutes
Sum(21) = 21t
New sum = 21t-66+52 = 21t-14
Hence new mean = 21t-14 / 21 = t-2/3

Hence B


stonecold how from this 21t-14 / 21 you got t-2/3 , I understand you divided by 7 , but there are two 21 :? could you write in detail :)
1 KUDOS received
BSchool Forum Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 2820
Location: India
GPA: 3.12
Premium Member
The average (arithmetic mean) length per film for a group of 21 films [#permalink]

Show Tags

New post 06 Mar 2018, 11:18
1
dave13 wrote:
stonecold wrote:
Great Solutions above.
Here is my solution =>
Average length = t minutes
Sum(21) = 21t
New sum = 21t-66+52 = 21t-14
Hence new mean = 21t-14 / 21 = t-2/3

Hence B


stonecold how from this 21t-14 / 21 you got t-2/3 , I understand you divided by 7 , but there are two 21 :? could you write in detail :)


Hey dave13

\(\frac{21t-14}{21} = \frac{21t}{21} - \frac{14}{21} = t - \frac{2}{3}\)

Hope that helps
_________________

You've got what it takes, but it will take everything you've got

The average (arithmetic mean) length per film for a group of 21 films   [#permalink] 06 Mar 2018, 11:18
Display posts from previous: Sort by

The average (arithmetic mean) length per film for a group of 21 films

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


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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®.