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    Question

    In an arithmetic progression, the first term is 4 and

    the sum of the first 20 terms is 650. Find the common difference.
    A 2 Correct Answer Incorrect Answer
    B 1 Correct Answer Incorrect Answer
    D 3 Correct Answer Incorrect Answer

    Solution

    For AP, sum of n terms: Sₙ = (n/2)[2a + (n − 1)d] Given: n = 20, a = 4, Sₙ = 650 650 = (20/2)[2×4 + 19d] 650 = 10[8 + 19d] Divide both sides by 10: 65 = 8 + 19d 19d = 65 − 8 = 57 d = 57 / 19 = 3

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