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# The average age of 30 students of a class is 12 years. The average age

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Math Expert
Joined: 02 Sep 2009
Posts: 58452
The average age of 30 students of a class is 12 years. The average age  [#permalink]

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21 Feb 2019, 00:43
00:00

Difficulty:

25% (medium)

Question Stats:

82% (01:23) correct 18% (01:59) wrong based on 17 sessions

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The average age of 30 students of a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another group of 5 of them is 14 years. What is the average age oi the remaining students?

A. 8
B. 9
C. 10
D. 12
E. 13

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Re: The average age of 30 students of a class is 12 years. The average age  [#permalink]

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21 Feb 2019, 03:49
1
Bunuel wrote:
The average age of 30 students of a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another group of 5 of them is 14 years. What is the average age oi the remaining students?

A. 8
B. 9
C. 10
D. 12
E. 13

Average of 30 = 12
total of 30 students = 12*30 = 360

Average of 5 students = 10
Total of 5 students = 10*5 = 50

Average of other 5 students = 14
Total of other 5 students = 14*5 = 70

Age of remaining 20 (=30-5-5) students = 360 - 50 - 70 = 240

Average of remaining 20 students = 240/20 = 12

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Re: The average age of 30 students of a class is 12 years. The average age  [#permalink]

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21 Feb 2019, 09:20
Bunuel wrote:
The average age of 30 students of a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another group of 5 of them is 14 years. What is the average age oi the remaining students?

A. 8
B. 9
C. 10
D. 12
E. 13

total age of class= 12*30 ;360
of first group ; 5*10 ; 50 ; 310
and 2nd group ; 5*14 ; 70 ; 240
so 240/20 ; 12
IMO D
Re: The average age of 30 students of a class is 12 years. The average age   [#permalink] 21 Feb 2019, 09:20
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