Multiple choice

Find the sum of first 20 even terms of the arithmetic sequence.

  1. $420$
  2. $401$
  3. $402$
  4. $403$
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A Correct answer
AI explanation

Assuming the standard arithmetic sequence of natural numbers, the first 20 even terms form the sequence 2, 4, 6, ..., 40. This sequence has 20 terms, so using the sum formula for an arithmetic progression, S_n = n/2(a + l), we get S_20 = 20/2(2 + 40). Calculating this gives 10 * 42, which equals 420.

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