Question

how many 2 digit numbers can be formed using only the digits 2, 3, 5, and 6, if the digits are not be repeated within a number

Answer 1

23
25
26
32
35
36
52
53
56
62
63
65

Answer 2

12

Explanation:

You want the number of two digit numbers that can be made from the digits {2, 3, 5, 6} if there are no repeats.

Permutations

The first digit can be any of the four.

The second digit can be any of the remaining three, so there are ...

4×3 = 12 possible 2-digit numbers

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Additional comment

They are ...

23, 25, 26, 32, 35, 36, 52, 53, 56, 62, 63, 65