Question

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.​

Answer 1

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