ACT Math Practice Question #1440 (Medium (31)) | Test Citadel
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ACT Math Difficulty: Medium (31)

Digital ACT Math Practice Question #1440

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What is the sum of the first 20 terms of the arithmetic sequence defined by a_n = 4n - 1?
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S_20 = 10 * (3 + 79) = 820.

Masterclass Solution & Distractor Trap Analysis

A_1 = 4(1) - 1 = 3. a_20 = 4(20) - 1 = 79. S_20 = 20 * (a_1 + a_20) / 2 = 10 * (3 + 79) = 10 * 82 = 820....

Distractor Analysis: Trap choice eliminates careless test-takers who confuse roots with coordinates...

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