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    Question

    The average weight of 12 students in a dance class is 45

    kg. If the weight of 3 instructors is also included, then the new average weight of each person (instructor + student) in the dance class becomes 50 kg. Find the average weight of the three instructors.
    A 20 kg Correct Answer Incorrect Answer
    B 80 kg Correct Answer Incorrect Answer
    C 50 kg Correct Answer Incorrect Answer
    D 70 kg Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the average weight of the three instructors be 'x' kg. So, total weight of the three instructors = 3 × x = '3x' kg. ATQ: 45 × 12 + '3x' = 50 × (12 + 3) Or, 540 + 3x = 50 × 15 Or, 540 + 3x = 750 Or, 3x = 750 - 540 = 210 Or, x = 210 ÷ 3 = 70 Therefore, the average weight of the three instructors is 70 kg.

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