Q3.The phone number in one region is designed to have 8 digits. The first digit can not be zero. 1.How many different phone numbers are possible? 2. Randomly select one phone number, what is the probability that it starts with number 6? 3. Randomly select one phone number, what is the probability that all 8 digits are different numbers?
Q3.The phone number in one region is designed to have 8 digits. The first digit can not be zero.
1.How many different phone numbers are possible?
2. Randomly select one phone number, what is the
3. Randomly select one phone number, what is the probability that all 8 digits are different numbers?
According to the sum, The phone number in one region is designed to have 8 digits. The first digit can not be zero.
So, the first digit of the phone number has to be anyone from 1 to 9. We can choose it in ways.
1.The no. of different phone numbers that are possible is-3
the first digit of the phone number has to be anyone from 1 to 9. We can choose it in ways.
The rest of the places can be filled with any of the 10 digits(0-9). So, in 107 ways.
Thus, the total number of possible phone numbers is .
2. Randomly select one phone number, the probability that it starts with number 6 is-
The first place will be 6. So, the possible way is 1. For the rest of the 7 places, they can be selected from 0-9, in107 ways.
So, the probability that it starts with number 6 is=
=
=0.1112
Hence, the probability that it starts with number 6 is-0.1112.
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