How many four digit even numbers can be formed using the digits {2, 3, 5, 1, 7, 9}

A. 60
B. 360
C. 120
D. 240

Explanation:

The given digits are 1, 2, 3, 5, 7, 9

A number is even when its units digit is even. Of the given digits, two is the only even digit.
Units place is filled with only ‘2’ and the remaining three places can be filled in ⁵P₃ ways.
Number of even numbers = ⁵P₃ = 60.