Question:
Set $S$: five-digit numbers from digits 1–5 exactly once, exactly 2 odd positions have odd digits. Find sum of rightmost digits of all numbers in S.
Set $S$: five-digit numbers from digits 1–5 exactly once, exactly 2 odd positions have odd digits. Find sum of rightmost digits of all numbers in S.
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Symmetry in permutations simplifies sum over positions.
Updated On: Jul 31, 2025
- 228
- 216
- 294
- 192
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The Correct Option is A
Solution and Explanation
By symmetry, each allowed digit appears equal times in units place. Count arrangements per digit, multiply by digit value, sum. Calculation yields 228.
\[
\boxed{228}
\]
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