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    Question

    Each member of a picnic party contributed twice to their

    serial number. The total collection was Rs 3042. The (approximate) number of members present in the party was
    A 55 Correct Answer Incorrect Answer
    B 32 Correct Answer Incorrect Answer
    C 42 Correct Answer Incorrect Answer
    D 39 Correct Answer Incorrect Answer

    Solution

    Let the number of members be n.

    Then their serial numbers are: 1, 2, 3, ..., n.

    Each member contributes 2 × their serial number,
    So, total contribution is: 2(1 + 2 + 3 +…+ n)
    We know that sum of n natural numbers = n (n + 1)/2
    So, 2 x n(n + 1)/2 = 3042
    n(n + 1) = 3042
    by solving this equation, we get n = 54.665

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