Number of Numbers
Probability
Level
3
How many 4 digit numbers can be made with the digits 1, 2, 3, and 4 such that no two adjacent digits are same?
The answer is 108.
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1 solution
First we can put any four options hence we have 4 options. Then 3 options are left as we cannot repeat the one we have already used. Hence 3 options. And then again 3 options as we have used the two and we have a no which is beside us so we cannot repeat that no Hence again we have 3 options .. and again 3 options. Hence 4 ∗ 3 ∗ 3 ∗ 3 = 108 . That is our answer