Question
Font the sum of the first 20 term of an arithmetic series whses first term is 7 and last term 35
Answers
GPT-4o mini
To find the sum of the first 20 terms of an arithmetic series where the first term (\(a\)) is 7 and the last term (\(l\)) is 35, we can use the formula for the sum of the first \(n\) terms of an arithmetic series:
\[
S_n = \frac{n}{2} \times (a + l)
\]
Here, \(n = 20\), \(a = 7\), and \(l = 35\).
Substituting the values into the formula, we get:
\[
S_{20} = \frac{20}{2} \times (7 + 35)
\]
\[
S_{20} = 10 \times (42)
\]
\[
S_{20} = 420
\]
Thus, the sum of the first 20 terms of the arithmetic series is **420**.
\[
S_n = \frac{n}{2} \times (a + l)
\]
Here, \(n = 20\), \(a = 7\), and \(l = 35\).
Substituting the values into the formula, we get:
\[
S_{20} = \frac{20}{2} \times (7 + 35)
\]
\[
S_{20} = 10 \times (42)
\]
\[
S_{20} = 420
\]
Thus, the sum of the first 20 terms of the arithmetic series is **420**.