Rata-rata 12 bilangan adalah 15 . rata-rata 4 bilangan pertama sama dengan 10,rata rata enam bilangan berikutnya 20. Tentukan rata-rata 2 bilangan yang tersisa

jawab

12 (15) = 4(10) + 6(20) + 2 X
180 = 40 + 120 + 2x
180 =  160 + 2x
2x = 20
x = 10

x1 = 10
n1 = 4
x2 = 20
n2 = 6
n3 = 2
n total = 12
x total = 15
x3 = ....?


x total = [(x1 . n1) + (x2 . n2) + (x3 . n3)] ÷ n total
15 = (40 + 120 + 2x) ÷ 12
15 × 12 = 160 + 2x
180 = 160 + 2x
2x = 20
x = 10