How many 4-digit numbers that are divisible by 4 can be formed using the digits 1, 2, 3 and 4 (repetition of digits is <strong>NOT</strong> allowed)?

Explanation

A number is divisible by 4 if the number formed by its last two digits is divisible by 4. The possible pairs from the given digits without repetition are 12, 24, and 32. For each of these 3 combinations of last two digits, the remaining 2 digits can be placed in the first two positions in 2! = 2 ways. Total valid numbers = 3 \times 2 = 6.

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