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    Question

    If '63a9b' is a five-digit number which is divisible by

    72, then find the value of (a + 2b).
    A 20 Correct Answer Incorrect Answer
    B 11 Correct Answer Incorrect Answer
    C 24 Correct Answer Incorrect Answer
    D 18 Correct Answer Incorrect Answer

    Solution

    We are given 63a9b is divisible by 72, so it must be divisible by 8 and 9. Divisible by 8 → last 3 digits (a9b) must be divisible by 8 Try values → a = 7, b = 2 gives 792, and 792 ÷ 8 = 99 ✅ Divisible by 9 → sum of digits: 6 + 3 + 7 + 9 + 2 = 27, which is divisible by 9 ✅ So the number is 63792 → a = 7, b = 2 → a + 2b = 7 + 4 = 11

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