GATE 2023 IN – Question 49
How many five-digit numbers can be formed using the integers 3, 4, 5 and 6 with exactly one digit appearing twice?
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Show answer and explanation
Correct answer: 240 to 240
Explanation
Choose the repeated digit in 4 ways. Arrange five digits with exactly one repeated pair in $5!/2!=60$ ways. No digit is zero, so there is no leading-zero restriction. Total $4(60)=\boxed{240}$.