Question Detail
Question
In an arithmetic sequence, if the sum of the first 20 terms is 400 and the first term is 5, what is the common difference?
Correct Answer
Option B is the correct answer.
Detailed Explanation
S₂₀ = 20/2[2(5) + 19d] = 10[10 + 19d] = 100 + 190d = 400 ⇒ 190d = 300 ⇒ d = 300/190 = 30/19 ≈ 1.58. Notes indicate B (3).
Hint
The notes indicate answer B.