How many possible numbers can be there??

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empt3a

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If the mobile number is consist of 10 digits. Where the first 5 digits is area code then how many possible number can be there? The first 5 numbers are 98029.
 
If there are no constraints on the last 5 digits, just ask yourself, How many 5-digit numbers are there?
 
empt3a said:
So there is constraints in last 5 digits because it is mobile number. Mobile number can be anything between 0-9 no matter whether they repeat or not.
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The statements "there is constraints" and "number can be anything between 0-9 no matter whether they repeat or not" seem somewhat contradictory to me.
 
Do you know what I mean by constraint? If there are no constraints, then, as you say, each digit can be anything. A constraint might be, for example, that the first digit can't be zero, or that a digit can't appear twice.

If each digit can be anything from 0 to 9, then these five digits can be anything from 00000 to 99999. How many numbers are there?
 
empt3a said:
So there is constraints in last 5 digits because it is mobile number. Mobile number can be anything between 0-9 no matter whether they repeat or not.
Click to expand...
The issue here is that you think that there are some phone numbers that can not be allowed. I tend to agree with you. For example I never saw a phone number that starts with 0 or 1. In the US, no phone numbers start with 911 as that is our emergency number.
So yes, there are restrictions. But the problem that you posted I assume is a probability question. In that case you can only assume the restrictions that are stated in the problem. So if there is no mentioning that 0 or 1 can NOT be in the number then you assume it can. Do not put your personal knowledge into the problem. The restriction are only the ones listed. Of course you have to use the fact that the digits are 0-9.
 
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