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# Exams

Author Message
TAGS:
Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 563
Location: United Kingdom
GMAT 1: 730 Q49 V40
GPA: 2.9
WE: Information Technology (Consulting)
Followers: 21

Kudos [?]: 994 [0], given: 217

Exams [#permalink]  18 Nov 2011, 13:02
00:00

Difficulty:

(N/A)

Question Stats:

50% (01:03) correct 50% (01:39) wrong based on 6 sessions
The average score of x number of exams is y. When an additional exam of score z is added in, does the average score of the exams increase by 50%?
(1) 3x = y
(2) 2z - 3y = xy

For me its E. Can someone please confirm?
_________________

Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Current Student
Joined: 08 Jan 2009
Posts: 330
GMAT 1: 770 Q50 V46
Followers: 23

Kudos [?]: 105 [2] , given: 7

Re: Exams [#permalink]  19 Nov 2011, 04:40
2
KUDOS
Restate the question as variables:

is (xy + z)/(x+1) = 1.5y?
xy + z = 1.5xy + 1.5y
.5xy = z - 1.5y
xy = 2z - 3y

1) No idea what number z is - NS
2) 2z - 3y = xy - Sufficient as per restatment

B

Another way to think of this is to try some numbers. Clearly A is insufficient we need to know something about z, but with 2), you could try something like the following:

assume x = 1, y = 1, by 2) z must = 2
average before: 1, average after: 3 / 2 = 1.5. Exactly 50% increase.

assume x = 2, y = 4, by 2) z = 10
average before: 8 / 2 = 4, average after 18 / 3 = 6. Exactly 50% increase.

Seems safe to go with B.
Re: Exams   [#permalink] 19 Nov 2011, 04:40
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