arithmetic series

Question

find the sum of the first 25 terms:

2, 8, 14, 20

Answer 1

Sum of arithmetic sequence is "Sn"

Sn = [n(a + an)]/2

Arithmetic equation = addition/subtraction is the common connection between terms.

2, 8, 14, 20... each term is 6 more than the previous.

To find the 25th term...

an = a1 + (n-1)*d

d = common connection (not the actual term for it, but makes sense I think)

n = term in sequence you are finding

a1 = first term in the sequence

a25 = 2 + (25 - 1)*6

a25 = 146

S25 = [25(2 + 146)]/2

=(25*148)/2

Answer 2

the formula is

n = 25; a1 = 2; d = 6

the sum = 25/2 * [2*2 + (25-1)*(6)] = 12.5 * [4 + 144] = 1850