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GRE Math Challenge #65-When 9 students took a zoology quiz
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03 May 2015, 01:20
03 May 2015, 01:20
Expert Reply
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Question Stats:
71% (00:37) correct
28% (01:23) wrong based on 14 sessions
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When 9 students took a zoology quiz with a possible score of 0 to 10, inclusive, there average (arithmetic mean) score was 7.5. If a tenth student takes the same quiz, what will be the least possible average score on the quiz for all 10 students?
A. 6.5
B. 6.75
C. 7.0
D. 7.25
E. 7.5
A. 6.5
B. 6.75
C. 7.0
D. 7.25
E. 7.5
Re: GRE Math Challenge #65-When 9 students took a zoology quiz
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18 Jul 2016, 04:45
18 Jul 2016, 04:45
Option (B) 6.75
9*7.5=67.5
if tenth scores 0
(67.5+0)/10=6.75 !
9*7.5=67.5
if tenth scores 0
(67.5+0)/10=6.75 !
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Re: GRE Math Challenge #65-When 9 students took a zoology quiz
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21 Jul 2016, 09:51
21 Jul 2016, 09:51
1
sandy wrote:
When 9 students took a zoology quiz with a possible score of 0 to 10, inclusive, there average (arithmetic mean) score was 7.5. If a tenth student takes the same quiz, what will be the least possible average score on the quiz for all 10 students?
A. 6.5
B. 6.75
C. 7.0
D. 7.25
E. 7.5
A. 6.5
B. 6.75
C. 7.0
D. 7.25
E. 7.5
Average score for 9 students = 7.5
In other words, (SUM of the 9 scores)/9 = 7.5
This means that SUM of the 9 scores = (7.5)(9) = 67.5
We want to MINIMIZE the average score when a 10th student writes the test.
To do this, let's give the student a score of 0.
When we add a score of 0 to the current SUM, we get 67.5 + 0 = 67.5
So, average score of 10 students = (SUM of the 10 scores)/10
= 67.5/10
= 6.75
Answer:
Show: ::
B
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