Question

What is the number of combinations on a lock. (for a 40-number lock, no successive repeating numbers)

(permutations or combinations).

Answer 1

64,000 different combinations
The lock in the challenge requires that you choose from 40 different numbers, three different times. Therefore, there are 40 × 40 × 40, or 64,000 different combinations.

Answer 2

The lock in the challenge requires that you choose from 40 different numbers, three different times. So then there would be 40 × 40 x 40, or 64,000 different combinations.