Jawabanmu

2014-05-21T16:58:07+07:00
1.
Bilangan itu adalah : 105, 110, 115, ....., 295
a = 105, b = 5,

Un = a + (n-1)b
295 = 105 + (n-1)5
295 = 105 + 5n - 5
295 = 100 + 5n
5n = 295 - 100
5n = 195
n = 39

Sn = 1/2 n (a + Un)
.....= 1/2 x 39 x (105 + 295)
.....= 39/2 x 400
Sn = 7800

2.
n = 8
rata2 = 40/8 = 5

∑(Xi - rata2)^2 = (2 - 5)^2 + (3 - 5)^2 + (5 - 5)^2 + (6 - 5)^2 + (4 - 5)^2 + (7 - 5)^2 + (8 - 5)^2 + (5 - 5)^2
= 28

S^2 = 1/5 . 28
= 28/5

Simpangan Baku (S) = akar S^2 = √28/5 
                                                = 2/5 √35