Solve the problem.
-If $\mathrm { a } _ { 1 }$ is $- 10$ and $\mathrm { d }$ is 3 , find $\mathrm { S } _ { 55 }$.
A) 3625
B) 3905
C) 3834
D) 3988

Question

Quizplus · Accepted Answer

The sum of an arithmetic series can be found using the formula $S_n = \frac{n}{2}[2a_1 + (n-1)d]$, where $S_n$ is the sum of the first $n$ terms, $a_1$ is the first term, $d$ is the common difference, and $n$ is the number of terms. Plugging in the given values ($a_1 = -10$, $d = 3$, $n = 55$), we get $S_{55} = \frac{55}{2}[2(-10) + (55-1)3] = \frac{55}{2}[-20 + 162] = \frac{55}{2} \times 142 = 55 \times 71 = 3905$.

Solve the Problem a1\mathrm { a } _ { 1 }a1​

Solve the Problem $\mathrm { a } _ { 1 }$