22. The mean age of 40 students is 16 years and the mean
age of another group of 60 students is 20 years. Find
out the mean age of all the 100 students combined
together:
(A) 18.4
(B) 19
(C) 19.6
(D) 20
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here it is given that
mean age of 40 students is 16 thus,
sum of observations
——————————— = mean
no. of students
sum of observations
———————————= 16.
40
sum of observations = 16×40. = 640
for the other group
sum of observations.
——————————— = mean
no. of students
sum of observations
——————————— = 20
60
sum of observations = 20 ×60 = 1200
mean age of all the hundred students
= sum of observations of the first group + sum of observations of second group
—————————————————————————
no. of students
=. 640+1200. 1840.
———————. = ———— = 18.4
100. 100
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