3. A person has to choose two-digits from 1, 2, 3 and 4 numbers to make two digit number. How many different arrangements of the digits are possible if repetition is allowed?
to find the answer, solve it by using permutation then you'll be having 4P2 which is 4×3×2×1 / 2×1 = 12 and since repetition is allowed, add 4 to 12 and you'll get 16