What is the mean age of all students of the city's schools?

(1) The average age of the students in each of the city's schools is 12
(2) The number of students in each of the city's schools is 70
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If the average at each school is the same, then the overall average will be equal to the average at each school, so S1 is sufficient and the answer should be A.
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Let there be 2 schools A and B
To find. Mean age = sum of ages of students in A and B / sum of number of students in A and B
= age A + age B/ no. A + no. B

1. The average age of the students in each of the city's schools is 12.
We have two schools A and B.
For A.
Avg1 = sum of ages of student in school A/ no. of student in school A
12 = sum of ages of student in school A/ no. of student in school A

sum of ages of student in school A = 12 * no. of student in school A

Avg2=sum of ages of student in school B/ no. of student in school B
12 = sum of ages of student in school B/ no. of student in school B

sum of ages of student in school B = 12 * no. of student in school B

Mean Age=sum of ages of student in school A+sum of ages of student in school B /no. of student in school A+ no. of student in school B
= 12 * no. of student in school A + 12 * no. of student in school B/no. of student in school A+ no. of student in school B
=12(no. of student in school A + no. of student in school B)/no. of student in school A+ no. of student in school B
=12.

Sufficient.

2. The number of students in each of the city's schools is 70.
Mean Age=sum of ages of student in school A+sum of ages of student in school B /no. of student in school A+ no. of student in school B
= sum of ages of student in school A+sum of ages of student in school B /70+70
=sum of ages of student in school A+sum of ages of student in school B /140.

sum of ages of student in school A+sum of ages of student in school B --we do not know this.

Insufficient.

OA A.
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What a question ! :D

if average age of students at each school is 12.. that means..mean of every school will be ..

for example..there are 5 schools...(12,12,12,12,12) there means will be 12..
Ans is A..

statement 2..is insufficient..
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