Back to Derive geometric series formula — Problem 4 · Task Set 8

Exercises: Geometric Series Formula

For each problem, identify the parameters a, r, and n before applying any formula. Always check whether r = 1. Show your work for computation problems.

Grade 9·22 problems·~45 min·Common Core Math - HS Algebra·standard·hsa-sse-b-4

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Fluency Practice

What is the sum of the geometric series $7 + 7 + 7 + 7 + 7 + 7$ (six terms)?

$\dfrac{7(1 - 1^6)}{1 - 1} = \dfrac{0}{0}$ , which is undefined.

$7^6 = 117649$

$S = na = 6 \times 7 = 42$

$S = 7 \times 6^1 = 42$ using the formula.