the average marks of 50 student of a class have 54. if 20 student od the class have average mark 60. find average marks of remaining student.
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Answer:
11.5
Step-by-step explanation:
Here,
n1=10,x1=60 and σ1=4
∴ ∑xi=60×10=600
Now, n2=10,x2=40 and σ2=6
∴ ∑xi=10×40=400
⇒ Total marks of 20 students (∑x)=400+600=1000
⇒ x=201000=50
Now, σ12=(4)2
⇒ n11∑110xi2−(x1)2=16
⇒ ∑110xi2=n
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