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    Question

    In a gathering of 30 guests, the average age of each

    guest in the class is 21 years. Later, 4 more guests join the party, causing the average age of the entire party to decrease by 12 months. Determine the average age of the 4 guests who joined the class.
    A 5 yrs Correct Answer Incorrect Answer
    B 25.2 yrs Correct Answer Incorrect Answer
    C 12.5 yrs Correct Answer Incorrect Answer
    D 15.55 yrs Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

    ATQ, Initial sum of ages of the guest in the party = 21 × 30 = 630 years New average age of the guest = 21 - (12/12) = 21 - 1 = 20 years New sum of ages of the guest in the party = 20 × 34 = 680 years So, the sum of ages of the guest who joined the party = 680 - 630 = 50 years So, the required average = (50/4) = 12.5 years

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