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    Question

    Two years hence, the ratio of the ages of β€˜B’ and

    β€˜C’ will be 5:4. The present age of β€˜C’ is half of the sum of the present ages of β€˜A’ and β€˜B’. Three years ago, the product of the ages of β€˜A’ and β€˜C’ (in years) was 77. If the age of β€˜B’ eight years hence from now will be β€˜p’ years, then how many statement(s) among the following is/are true about β€˜p’? Statement I: β€˜p’ is a perfect square. Statement II: (p βˆ’ 2) is a prime number. Statement III: (p + 3) is completely divisible by 6. Statement IV: (p + 5) > 28
    A 2 Correct Answer Incorrect Answer
    B 4 Correct Answer Incorrect Answer
    D 3 Correct Answer Incorrect Answer
    E 1 Correct Answer Incorrect Answer

    Solution

    Let the ages of β€˜B’ and β€˜C’ two years hence from now be β€˜5k’ years and β€˜4k’ years respectively. Present age of β€˜B’ = (5k βˆ’ 2) years Present age of β€˜C’ = (4k βˆ’ 2) years So, present age of β€˜A’ = 2 Γ— (4k βˆ’ 2) βˆ’ (5k βˆ’ 2) = (3k βˆ’ 2) years Now, (3k βˆ’ 2 βˆ’ 3) Γ— (4k βˆ’ 2 βˆ’ 3) = 77 Or, (3k βˆ’ 5) Γ— (4k βˆ’ 5) = 77 Or, 12kΒ² βˆ’ 15k βˆ’ 20k + 25 = 77 Or, 12kΒ² βˆ’ 35k βˆ’ 52 = 0 Or, (12k + 13)(k βˆ’ 4) = 0 So, β€˜k’ = βˆ’(13/12) or β€˜k’ = 4 But β€˜k’ cannot be negative. So, β€˜k’ = 4 Therefore, β€˜p’ = (5k βˆ’ 2) + 8 = 5k + 6 = 26 Statement I 26 is not a perfect square.
    So, statement I is false. Statement II 26 βˆ’ 2 = 24, which is not prime.
    So, statement II is false. Statement III 26 + 3 = 29, which is not completely divisible by 6.
    So, statement III is false. Statement IV 26 + 5 = 31 > 28.
    So, statement IV is true. Therefore, one among the four statements given is true. Hence, option E.

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