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# The average number of students per class at School X is 25 and the ave

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Manager
Joined: 14 Feb 2016
Posts: 71
The average number of students per class at School X is 25 and the ave  [#permalink]

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10 Jan 2019, 03:06
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Difficulty:

55% (hard)

Question Stats:

63% (01:36) correct 37% (01:55) wrong based on 85 sessions

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The average number of students per class at School X is 25 and the average number of students per class at School Y is 33. Is the average number of students per class for both schools combined less than 29?

1) There are 12 classes in school X.
2) There are more classes in school X than in school Y.

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Manager
Joined: 01 May 2017
Posts: 82
Location: India
The average number of students per class at School X is 25 and the ave  [#permalink]

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10 Jan 2019, 05:51
The average number of students per class at School X is 25 and the average number of students per class at School Y is 33. Is the average number of students per class for both schools combined less than 29?

(33+25)/2 = 29
At least equal number of students per class in school x and equal number of students per class in school y should be present for combined average to be 29
OR
Y >x

1) There are 12 classes in school X.
Insufficient

2) There are more classes in school X than in school Y.
From above explanation X > Y, implies avg of students both classes combines is < 29
Sufficient

Option B is correct
Manager
Joined: 04 Oct 2017
Posts: 81
Re: The average number of students per class at School X is 25 and the ave  [#permalink]

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16 Jan 2019, 20:40
Dare Devil wrote:
The average number of students per class at School X is 25 and the average number of students per class at School Y is 33. Is the average number of students per class for both schools combined less than 29?

(33+25)/2 = 29
At least equal number of students per class in school x and equal number of students per class in school y should be present for combined average to be 29
OR
Y >x

1) There are 12 classes in school X.
Insufficient

2) There are more classes in school X than in school Y.
From above explanation X > Y, implies avg of students both classes combines is < 29
Sufficient

Option B is correct

Hi,

Can you please elaborate on the explanation??? I am lost. I did not understand how did you arrive at the conclusion that since x>y the average is <29.
Manager
Joined: 01 May 2017
Posts: 82
Location: India
Re: The average number of students per class at School X is 25 and the ave  [#permalink]

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16 Jan 2019, 22:28
1
Kezia9 wrote:
Dare Devil wrote:
The average number of students per class at School X is 25 and the average number of students per class at School Y is 33. Is the average number of students per class for both schools combined less than 29?

(33+25)/2 = 29
At least equal number of students per class in school x and equal number of students per class in school y should be present for combined average to be 29
OR
Y >x

1) There are 12 classes in school X.
Insufficient

2) There are more classes in school X than in school Y.
From above explanation X > Y, implies avg of students both classes combines is < 29
Sufficient

Option B is correct

Hi,

Can you please elaborate on the explanation??? I am lost. I did not understand how did you arrive at the conclusion that since x>y the average is <29.

(33+25)/2 = 29
At least equal number of students per class in school x and equal number of students per class in school y should be present for combined average to be 29
OR
Y >x

you add 25 and 33 can then sum is 29, which is towards 33(more value) in same way (33+25)/2 = 29 if you add more 25's the weightage of the overall average moves towards 25 < 29 (towards the less value)

example:
School X has 3 classes and school Y has 1, then the average will be < 29 (as along as 25's and 33's are equal the average remains at 29, because 33-25 = 8, now we distribute 4 equally i.e., 25+4 = 33-4 but once the Class of X are more than Classes of Y Overall average reduces from 29 moves towards 27

School X has 3 classes and school Y has 1, then the average will be < 29
(25*3+33*1)/29 = 27 < 29

Simple logic is if we have more 25's overall average moves towards it (<29), if more 33 it moves towards it (> 29) from their average (33+25)/2 = 29

Hope it's clear Now
Re: The average number of students per class at School X is 25 and the ave   [#permalink] 16 Jan 2019, 22:28
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