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# Some of the students enrolled at college T are part-time

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Director
Joined: 01 May 2007
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Some of the students enrolled at college T are part-time [#permalink]

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Updated on: 21 Oct 2014, 23:11
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Question Stats:

80% (00:53) correct 20% (00:43) wrong based on 264 sessions

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Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

Originally posted by jimmyjamesdonkey on 26 Apr 2008, 16:51.
Last edited by WoundedTiger on 21 Oct 2014, 23:11, edited 1 time in total.
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Schools: CBS, Kellogg
Re: Some of the students enrolled at college T are part-time [#permalink]

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26 Apr 2008, 19:02
jimmyjamesdonkey wrote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

B

this is C-trap
2.
Number of students enrolled at T in 1999 = (p+f) [p=part-time students and f=full-time students]
So, full-time students in 1999 = f

Number of students enrolled at T in 2000 = 1.05(p+f),
so full-time students in 2000 = 1.05*f

%increase of fulltime student = [1.05*f -f]/f = 5%
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Re: Some of the students enrolled at college T are part-time [#permalink]

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26 Apr 2008, 20:44
jimmyjamesdonkey wrote:
incorrect.

sondenso wrote:
Number of
students enrolled at T in 2000 = 1.05(p+f),
so full-time students in 2000 = 1.05*f

I think this is error reasoning!
Let wait for another response. I am a little confused
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Re: Some of the students enrolled at college T are part-time [#permalink]

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26 Apr 2008, 22:51
There is no information about increase/decrease of part time students in either statement so my pick is E , let me know what is OA.

if you pick numbers lets say in 99

FullTime=700
partTime=300

in 2000

FullTime=750
partTime=300 (stays the same since 5% increase is all counted in Full Time students )

scenario 2

in 99
FullTime =1300
PartTime=700
in 2000
FullTime=1350
Partime=750

% increase of fulltime students gives different answer for both the scenarios and hence my answer is E
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Some of the students enrolled at college T are part-time [#permalink]

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Updated on: 11 Sep 2011, 00:43
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

Image:
Attachment:

GPrep_Full_time_students.jpg [ 70.77 KiB | Viewed 6658 times ]

Originally posted by DeeptiM on 10 Sep 2011, 05:15.
Last edited by fluke on 11 Sep 2011, 00:43, edited 1 time in total.
OA corrected.
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Joined: 03 Mar 2010
Posts: 31
Re: Gprep - Fulltime students!! [#permalink]

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11 Sep 2011, 01:30
1
vinayaerostar wrote:

Answer should be E, and if you want to find the% increase of some thing then in that case we need to have to 2 data available.
1. Change( which is thr in 1 part)
2. original value or the value of fall 1999

so only one information is available so answer is E.

hope it helps
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Posts: 1899
Re: Gprep - Fulltime students!! [#permalink]

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11 Sep 2011, 03:04
1
1
DeeptiM wrote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

CASE 1:

 Total Students Full-time students Part-time Students Fall 1999 100 10 90 Fall 2000 105 60 45 % Change 5% increase 50 more students, a 500% increase Not Required

CASE 2:

 Total Students Full-time students Part-time Students Fall 1999 100 25 75 Fall 2000 105 75 30 % Change 5% increase 50 more students, a 200% increase Not Required

Not Sufficient.

Ans: "E"
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Re: Some of the students enrolled at college T are part-time [#permalink]

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21 Oct 2014, 19:09
jimmyjamesdonkey wrote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

(1)

insufficient

(2)
no differentiation between part-time and full-time students
insufficient

(together)
we still don't know anything about the # of part-time students, which is an essential contributor to the 5% increase mentioned in statement (2)
examples:
- if there are 0 part-time students in both years, then the # of full-time students has increased by 5%
- if the # of full-time students has increased from 0 to 50 but the # of part-time students has remained constant at 1000 (so that 50 is 5 percent of the enrollment), then the # of full-time students has grown by infinity%
...and anything in between

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Posts: 38
Re: Some of the students enrolled at college T are part-time [#permalink]

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30 Sep 2016, 23:27
VeritasPrepKarishma, Bunuel, chetan2u
I did understood the solution and agree that answer should be E, but I also fall into trap of choosing B in the first go.
Could you please explain how to answer this question algebraically without taking numbers?
I am just not able to understand whats wrong with the approach of taking initial values to be X+Y and final values 1.05(X+Y)!
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Re: Some of the students enrolled at college T are part-time [#permalink]

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08 Oct 2016, 02:53
Hello Moderators,
any update on this one?
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GMAT 1: 770 Q51 V44
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Re: Some of the students enrolled at college T are part-time [#permalink]

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06 Feb 2017, 11:39
(1)
no indication of the size of the student body
insufficient

(2)
no differentiation between part-time and full-time students
insufficient

(together)
we still don't know anything about the # of part-time students, which is an essential contributor to the 5% increase mentioned in statement (2)
examples:
- if there are 0 part-time students in both years, then the # of full-time students has increased by 5%
- if the # of full-time students has increased from 0 to 50 but the # of part-time students has remained constant at 1000 (so that 50 is 5 percent of the enrollment), then the # of full-time students has grown by infinity%
...and anything in between

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Anaira Mitch

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Joined: 14 Nov 2012
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GMAT 1: 740 Q51 V38
Re: Some of the students enrolled at college T are part-time [#permalink]

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06 Sep 2017, 22:46
Sn: the new number of full time students.
So : the old number of full time students

The question is asking for Z as
Z = ( Sn - So) / So

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.

=> Sn - So = 50
We dont know So value so we cannot calculate Z.
Insuff.

2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

=> We have no clue whether an increase in the number of total student corellates with a rise in the number of full time students or not.
Insuff.

Posted from my mobile device
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Some of the students enrolled at college T are part-time [#permalink]

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23 May 2018, 19:05
Quote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

bumping gmatbusters niks18 amanvermagmat Bunuel VeritasPrepKarishma
for validating the approach/ suggesting an efficient one.

Step 1: simplify the questions stem to simplest form, I used algebraic approach to form linear equations.

Step 2: write algebraic form of equations for both the statements. As seen here, the main question asks for ratio of
difference of absolute values in numerator to the absolute value in denominator.
St 1 gives the difference, but the absolute value of denominator is not known.
St 2 seems to be providing no info in the context of what the question is asking.

Combining the statements, I still do not see arriving at an unique value for denominator, Hence (E)

Attachments

Q1.jpeg [ 32.98 KiB | Viewed 453 times ]

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Some of the students enrolled at college T are part-time [#permalink]

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26 May 2018, 21:30
1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
Since we do not know the number of full time students, this 50 can be very small or very large.
-if in 1999, there was only 1 full time student, and in 2000 number increased by 50, then no. of students = 51
% increase = $$\frac{50}{1}$$*100 = 5000%
-if in 1999, there were 1000 full time student, and in 2000 number increased by 50, then no. of students = 1050
% increase = $$\frac{50}{1000}$$*100 = 5%
Hence insufficient.

(PS: you need not do the above calculation. Remember since we do not know the base value, increase in value will never be sufficient to find the percentage increase.)

2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.
It is similar to St 1: since we don't know the initial total number of students, we can not find the number of total number/full time students.
hence insufficient.

Even after combining St 1 & 2, we are unable to find the number of full time students which is required to find the % increase in full time students. Hence NOT SUFFICIENT.

if we change the second statement as:

New Statement2):The number of full time students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.
Now find the number of Part time time students in 2000.

Quote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

bumping gmatbusters niks18 amanvermagmat Bunuel VeritasPrepKarishma
for validating the approach/ suggesting an efficient one.

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Re: Some of the students enrolled at college T are part-time [#permalink]

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26 May 2018, 21:52
1

Your equation for second statement is flawed, you forgot to put a bracket required to provide the effect of factor of 1.05.
See sketch.
Attachment:

Q1.jpeg [ 69.05 KiB | Viewed 386 times ]

now , even if you get correct equations, if you are not able to conclude further, it is not of much use.
In my opinion, this is not the best approach.

Quote:
Some of the students enrolled at college T are part-time students and the rest are full-time. By what percent did the number of full-time students enrolled at college T increase from fall of 1999 to the fall of 2000?

1) There were 50 more full-time students enrolled at college T in the fall of 2000 than in the fall of 1999.
2) The total number of students enrolled at college T increased by 5 percent from the fall of 1999 to the fall of 2000.

bumping gmatbusters niks18 amanvermagmat Bunuel VeritasPrepKarishma
for validating the approach/ suggesting an efficient one.

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Some of the students enrolled at college T are part-time [#permalink]

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26 May 2018, 23:03
Nice catch gmatbusters

Quote:
now , even if you get correct equations, if you are not able to conclude further, it is not of much use.

I have edited the steps in my original post to clear the fog.
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Some of the students enrolled at college T are part-time   [#permalink] 26 May 2018, 23:03
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