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    Question

    The average weight of 20 students in a class is 55 kg.

    If the weight of the class teacher is included, the average is increased by 0.5 kg. The weight of the class teacher is:
    A 67.2 kg Correct Answer Incorrect Answer
    B 63.5 kg Correct Answer Incorrect Answer
    C 65.5 kg Correct Answer Incorrect Answer
    D 68.4 kg Correct Answer Incorrect Answer

    Solution

    Let the weight of the teacher be 'x' kg. (Sum of total observations) = average × (Total number of observation) Total weight of all students = 55 x 20 = 1100 kg New average = 55 + 0.5 = 55.5 New observation when teacher included = 20 + 1 = 21 So, Total weight of all = 21 x 55.5 =1165.5 kg The weight of the teacher = (Total weight of all) - (Total weight of all students)   The required weight = 1165.5-1100 = 65.5kg

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