tentukan nilai x jika diketahui : a. nilai rata-rata = 6 nilai 4 5 6 7 8 9 frekuensi 5 x 12 8 3 2 b. nilai rata - rata = 44 nilai 30 35 40 45 5

a. nilai total = 4(5) + 5x + 6(12) + 7(8) + 8(3) + 9(2)
                   = 20 + 5x + 72 + 56 + 24 +18
                   = 190 +5x
jumlah data = 5 + x + 12 +8 + 3 +2 = 30 +x
rata rata = total /jumlah data
6 = (190 + 5x) / (30+ x)
180  + 6 x = 190 + 5x
x = 10


b. nilai total = 30(3) + 35(4) + 40(5) + 45(8) + 50x + 60(3)
                  = 970 + 50x
jumlah data = 3+4+5+8+x+3 = 23 + x
rata2 = 44
44 = (970 + 50x) / (23+x)
1012 + 44x = 970 + 50x
42 = 6x
x = 7