Permutations and Combinations

Question

The combinations of the gym lockers have 3 numbers from 0 to 9 inclusively. For example, one locker combination could be 338, 236, 244, or 111...

A) What is the maximum numbers of lockers possible in the school so that no two locks have the same combination?

B) If a combination is chosen at random from all the possible combinations, what is the probability that it will open a particular lock?

C) Each number contains the digit 3?

D) The first number is even, the second is odd and the third is 4?

Answer 1

Including 000 there are 1000 possible combinations.

Random choice: 1/1000

Digit 3: 3/10 [3xx, x3x, 3xx]

Specified sequence 1/40 [5,5,1]