Four digit numbers are formed by using the digits 1, 2, 3, 5 without repetition of digits. How many of them are divisible by 4?

Explanation

A number is divisible by 4 if the number formed by its last two digits is divisible by 4. Using the digits 1, 2, 3, 5, the only possible valid last two digits are 12, 32, and 52. For each of these 3 pairs, the remaining 2 digits can be arranged in the first two positions in 2! = 2 ways. Total combinations = 3 \times 2 = 6.

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