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Q. How many 4-digit numbers can be formed using the digits 0, 1, 2, 3, 4, 5 such that the number is a multiple of 4? (Repetitions of digits not allowed)
A.72
B.63
C.60
D.36
E.27
Number will be divisible by four if its last two digits are divisible by 4. So possible values of last two digits are 04,12,20,24,32,40,52
Now these number can be divided into two groups
a) when last two digits contain zero
b) when last two digits doesn't contain zero
a) when last two digit contains zero, let 4 digit number be abcd. now since cd are fixed. A, can take 4 values from the balance 4 numbers, and B can take 3 values from the remaining 3 numbers. Additionally, since 3 cases exists in which 0 comes in the last two digits. so total number of cases are
4.3.3 = 36 (first 4 for a, second 3 for b, and last 3 for remaining 2 digits)
b) when last two digits doesn't contains zero. In this case A can take 3 values (as zero cannot appear in the A, Why ? if we have zero in first place then number will become 3 digit number). B can have 3 values (as zero can come in this position), and there are 4 such cases in which 0 doesn't come in the last two digits. so total number of cases are
3.3.4 = 36
so overall cases = 36+36 = 72 hence A