Question 741042
The common difference is -2.5.
The first term is 6, so the nth term is -2.5n + 8.5 (please verify when n = 1).
To get the number of terms, we solve
-2.5n + 8.5 = -49
n = 23
The sum of the first n terms of an arithmetic sequence is equal to
{{{S[n] = (n/2)(a[1] + a[n])}}}
{{{S[n] = (23/2)(6 - 49)}}}
{{{S[n] = highlight(-494.5))}}}