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