Question

The mean of 20 observations is 30 and the mean of 30 observations is 40 then mean of all 50 observations is how much

Answer 1

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mean of 20 observation = 30

(a1+a2+..........+a20)/20 = 30

(a1+a2+.............+a20) = 30*20

sum of 20 observation = 600

mean of 30 observation = 40

(a1+a2+..........+a30)/30 = 40

(a1+a2+.............+a30) = 40*30

sum of 30 observation = 1200

            Sum of 50 observation = 1800

mean of 50 observation = 1800/50

                                         = 36 ans