nilai : 40, 50, 60, 70, 80, 90, 100 frekuensi : 2, 3, y, 8, 5, 4, 2 jika rata-rata nilai : 80 tentukan nilai y!

80 = 40×2 + 50×3 + 60× y + 70×8 +
80×5 + 90×4 + 100×2 ÷ 2 + 3 + y
+ 8 + 5 + 4 +2
80 = 80 + 150 + 60y + 560 + 400 +
360 + 200 ÷ 24 + y
80 (24 + y) = 4990 + 60y
1920 + 80y = 4990 + 60y
1920 - 4990 = 60y - 80y
- 3070 = -20y
y = - 3070 ÷ - 20
= 153,5