Find the sum of all four-digit numbers formed using the digits 1, 2, 4 and 6 (each used once).
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Correct answer: A. 86,658
Explanation
There are 4! = 24 numbers, and each digit appears 6 times in each place. Sum = (1 + 2 + 4 + 6) × 6 × 1111 = 13 × 6 × 1111 = 86,658.More Discrete Structures and Optimisation questions
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