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Problem #30 · August 26, 2026

Natural numbers

Find the sum of the smallest four-digit number with all distinct digits and the largest single-digit number.
  1. A10091009
  2. B10231023
  3. C10331033
  4. D12431243
  5. E10321032

WORKED EXAMPLE

Solution

To form the smallest four-digit number with all distinct digits, put 11 in the thousands place and 0,2,30, 2, 3 in increasing order in the remaining places: this gives 10231023. The largest single-digit number is 99. The sum is 1023+9=10321023 + 9 = 1032.
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