Credit cards place a three digit security code on the back of cards. What is the probability that a code starts with the number

The likelihood of a code commencing with the digit 7 is 1/10. There are a total of 10 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Moreover, the total number of possible codes formed using these digits is 1000, as there are 10 choices for the first, second, and third positions. This results in a total of 10×10×10=1000. If the first digit of the code is fixed as 7, we only need to choose digits for the second and third places. Thus, the total codes starting with the digit 7 equal 100, given that the first digit is set and we still have 10 options for both of the other digits (1×10×10=100). Therefore, the probability calculates as follows: Probability=100/1000=1/10.