Question

What is the sum of the arithmetic sequence 8, 14, 20 …, if there are 24 terms?

Answer 1

the sum is 6. An=8plus6 (n-1)

Answer 2

The answer is 1848

Sum of arithmetic sequence:
s = n(a1 + an)/2

n - number of terms
a1 - the first therm
an - n-th term

an = a1 + (n - 1)d
d - common difference

n = 24
a1 = 8
d = 6 (14 - 8 = 6; 20 - 14 = 6)
an = 8 + (24 - 1) * 6 = 8 + 23 * 6 = 146

s = n(a1 + an)/2
s = 24 * (8 + 146) / 2
= 24 * 154 / 2
= 1848