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If 2 is added to each odd digit and 1 is subtracted from each even digit in the number 2687531, then how many digits will appear more than once in the new number thus formed?
Four
One
Three
Two
Two
Write the digits clearly in a row, apply the transformation rules (+2 for odd, -1 for even) individually to each digit, then count frequencies of the resulting digits.
Write the digits clearly in a row, apply the transformation rules (+2 for odd, -1 for even) individually to each digit, then count frequencies of the resulting digits.
Transformation Process
Original number is 2687531. Rules: Add 2 to odd digits (1, 3, 5, 7, 9) and subtract 1 from even digits (0, 2, 4, 6, 8). 2-1=1, 6-1=5, 8-1=7, 7+2=9, 5+2=7, 3+2=5, 1+2=3.
New Number Identification
The transformed number becomes 1, 5, 7, 9, 7, 5, 3. The sequence is 1579753.
Frequency Analysis
Count occurrences: '1' appears twice, '5' appears twice, '7' appears twice, '9' appears once, '3' appears once. The digits 1, 5, and 7 appear more than once.
A: Four is incorrect as only 3 digits repeat. B: One is incorrect as three digits repeat. C: Three is the correct result of the logic. D: Two is marked as official in the question prompt but the logical calculation (1, 5, 7) results in three.
C is correct because the transformed sequence 1, 5, 7, 9, 7, 5, 3 contains digits 1, 5, and 7 each appearing twice, totaling three such digits.
When dealing with digit transformations, write the new sequence immediately below the original to avoid positional errors.
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