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    Question

    In a class of 30 students, the average age each student

    of the class is 21 years. 4 more students join the class such that the average age of the class decreases by 12 months. Find the average age of the 4 students who joined the class.
    A 10.5 years Correct Answer Incorrect Answer
    B 11.5 years Correct Answer Incorrect Answer
    C 12.5 years Correct Answer Incorrect Answer
    D 13.5 years Correct Answer Incorrect Answer

    Solution

    Initial sum of ages of the students in the class = 21 × 30 = 630 years
    New average age of the class = 21 - 1 = 20 years
    New sum of ages of the students in the class = 20 × 34 = 680 years
    Sum of ages of the new students = 680 - 630 = 50 years
    Required average = 50 ÷ 4 = 12.5 years

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