Question

Nilai rata-rata/mean : 5,5
nilai x ... ?

nilai : 3 , 4 , 5 , 6 , 7 , 8
frekuensi : 1 , 8 , 7 , 6 ,x , 3

Answer 1

Mean = (total nilai) / (total frekuensi)
5,5 = ((3*1)+(4*8)+(5*7)+(6*6)+(7*x)+(8*3)) / (1+8+7+6+x+3)
5,5 = (3 + 32 + 35 + 36 + 7x + 24) / (25 + x)
5,5 * (25 + x) = (130 + 7x)
137,5 + 5,5x = 130 + 7x
7,5 = 1,5x
5 = x