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A student took tests at the end of the academic year. After

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Current Student
Joined: 11 May 2008
Posts: 553
A student took tests at the end of the academic year. After [#permalink]

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28 Jul 2008, 18:53
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A student took tests at the end of the academic year. After the last test, his average score for all test increased from 85 to 86.7. How many tests did he take?
(1) The lowest score was 85.
(2) The score for the last test is 95.
A. Statement (1) ALONE is sufficient but Statement (2) ALONE is not sufficient.
B. Statement (2) ALONE is sufficient but Statement (1) ALONE is not sufficient.
C. BOTH Statements TOGETHER are sufficient, but NEITHER Statement alone is sufficient.
D. Each Statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
Director
Joined: 27 May 2008
Posts: 540

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28 Jul 2008, 19:46
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arjtryarjtry wrote:
A student took tests at the end of the academic year. After the last test, his average score for all test increased from 85 to 86.7. How many tests did he take?
(1) The lowest score was 85.
(2) The score for the last test is 95.
.

lets say he scored X in last test and there were N tests.... we have to find N=?

as per question stem
(N-1)*85 + X = N*86.7 ---------(1)

statement 1 : not suff
statement 2 : gives X, we can find out N from (1) ... suff .. Option B
Manager
Joined: 03 Jun 2008
Posts: 135
Schools: ISB, Tuck, Michigan (Ross), Darden, MBS

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28 Jul 2008, 19:56
durgesh79 wrote:
arjtryarjtry wrote:
A student took tests at the end of the academic year. After the last test, his average score for all test increased from 85 to 86.7. How many tests did he take?
(1) The lowest score was 85.
(2) The score for the last test is 95.
.

lets say he scored X in last test and there were N tests.... we have to find N=?

as per question stem
(N-1)*85 + X = N*86.7 ---------(1)

statement 1 : not suff
statement 2 : gives X, we can find out N from (1) ... suff .. Option B

That was a simple one, still goofed it up.
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Director
Joined: 27 May 2008
Posts: 540

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28 Jul 2008, 20:19
GMBA85 wrote:
That was a simple one, still goofed it up.

dont worry, happens to all of us....
SVP
Joined: 07 Nov 2007
Posts: 1789
Location: New York

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30 Jul 2008, 12:01
GMBA85 wrote:
durgesh79 wrote:
arjtryarjtry wrote:
A student took tests at the end of the academic year. After the last test, his average score for all test increased from 85 to 86.7. How many tests did he take?
(1) The lowest score was 85.
(2) The score for the last test is 95.
.

lets say he scored X in last test and there were N tests.... we have to find N=?

as per question stem
(N-1)*85 + X = N*86.7 ---------(1)

statement 1 : not suff
statement 2 : gives X, we can find out N from (1) ... suff .. Option B

That was a simple one, still goofed it up.

its better we goofed it up here.. ... --> We can learn from it..
other wise its more danger... will goofed it in real test.
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VP
Joined: 17 Jun 2008
Posts: 1373

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03 Aug 2008, 08:00
arjtryarjtry wrote:
A student took tests at the end of the academic year. After the last test, his average score for all test increased from 85 to 86.7. How many tests did he take?
(1) The lowest score was 85.
(2) The score for the last test is 95.
A. Statement (1) ALONE is sufficient but Statement (2) ALONE is not sufficient.
B. Statement (2) ALONE is sufficient but Statement (1) ALONE is not sufficient.
C. BOTH Statements TOGETHER are sufficient, but NEITHER Statement alone is sufficient.
D. Each Statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

I will go for B

average prev ,a1= 85
now a2=86.75 say number of tests = n

we get eqn :
(85n+x)/(n+1) = 86.7 where x is score in last test
(1) does not help giving x INSUFF
(2) helps giving value of x hnce solves this eqn and yields n SUFF

IMO B
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Re: avg DS   [#permalink] 03 Aug 2008, 08:00
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