Question

    If the 5-digit number 505xy is divisible by 11 and 21,

    then what is the value of (7x – 5y)?
    A 16 Correct Answer Incorrect Answer
    B 30 Correct Answer Incorrect Answer
    C 31 Correct Answer Incorrect Answer
    D 11 Correct Answer Incorrect Answer

    Solution

    LCM (11, 21) = 231 By taking the largest 5-digit number 50599 and divide it by 231. 50599 = 231(divisor) x 219(Quotient) + 10(rem) 50599 = 50589 + 10 50599-10 = 50589 (completely divisible by 231) 50589 = 505xy (where x = 8, y = 9) Now the value of (7x - 5y), (7x5y) = 7x8-5x9 =56-45 = 11 The value of (7x - 5y) is 11.

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