Question

Credit cards place a three digit security code on the back of cards. What is the probability that a code starts with the number 7?

Answer 1

Answer:

The probability that a code starts with the number 7 is:

                          1/10

Step-by-step explanation:

There are total 10 digits:

0   1   2    3    4   5   6   7   8   9

Also, the total number of codes that are possible using these digits are:

                            1000

( Since there are 10 choices for first place, 10 for second and 10 for third as well

Hence, total possibilities are: 10×10×10=1000 )

Also, if the first place of the code is fixed with number 7.

So, we need to chose the digits for second and third place.

Hence, total codes whose first digit is 7 are:

                      100

( Since the choice for first place is fixed and for second and third place we have 10 choices i.e. total such cases are: 1×10×10=100   )

Hence, the probability is calculated as:

            Probability=100/1000

                               =1/10