Arithmetic: Example 2

Arithmetic

Find S₇ for the arithmetic sequence 1, 4, 7, 10, 13 â€¦

Step 1. Determine the number of terms to add.

S₇ = a₁ + a₂ + a₃ + a₄ + a₅+ a₆ +a₇

Step 2. Continue the pattern to find the needed terms.

a ₆ = 16 and a₇ = 19

Step 3. Add the terms.

S₇ = 1 + 4 + 7 + 10 + 13 + 16 + 19

S₇ = 70