Matleena chooses three numbers at random from the numbers 1, 2, 3, 10. What is the probability that they are not all consecutive? (For example, the three numbers 6, 7, 8 are consecutive.)
The consecutive ones are
1 2 3
2 3 4
3 4 5
4 5 6
5 6 7
6 7 8
7 8 9
8 9 10
The number of possible combos = C(10,3) = 120
So the probability that they are not consecutive = 1 = P(that they are consecutive) =
1 -8/120 =
1 - 1/15 =
14 / 15
