Answer:
35 combinations
Step-by-step explanation:
The first digit cannot be 5 or 6 (Since the digits could not be in ascending order if that was the case).
If the first digit is 4, there is 1 possibility:
(4, 5, 6)
If the first digit is 3, there are 3 possibilities:
(3, 4, 5) (3, 4, 6) (3, 5, 6)
If the first digit is 2, there are 6 possibilities:
(2, 3, 4) (2, 3, 5) (2, 3, 6) (2, 4, 5) (2, 4, 6) (2, 5, 6)
If the first digit is 1, there are 10 possibilities :
(1, 2, 3) (1, 2, 4) (1, 2, 5) (1, 2, 6) (1, 3, 4) (1, 3, 5) (1, 3, 6) (1, 4, 5) (1, 4, 6) (1, 5, 6)
If the first digit is 0, there are 15 possibilities:
(0, 1, 2) (0, 1, 3) (0, 1, 4) (0, 1, 5) (0, 1, 6) (0, 2, 3) (0, 2, 4) (0, 2, 5) (0, 2, 6) (0, 3, 4) (0, 3, 5) (0, 3, 6) (0, 4, 5) (0, 4, 6) (0, 5, 6)
Therefore, he would need to try at most 35 combinations.
