Final answer:
The number of possible four-digit PIN codes with repetition allowed is 10,000, as there are 10 choices (0-9) for each digit and four positions to fill.
Step-by-step explanation:
The student is asking about the number of possible combinations for a four-digit pin number with repetition of digits allowed. Since each digit of the pin can be any number from 0 to 9, there are 10 choices for each position. To find the total number of possible combinations, we multiply the number of choices for each digit together:
10 choices for the first digit, 10 for the second digit, 10 for the third digit, and 10 for the fourth digit. Therefore, the calculation would be:
10 \(\times\) 10 \(\times\) 10 \(\times\) 10 = 10,000 combinations.