Quandaries and Queries


Who is asking: Student
Level: Secondary

How many number combinations are possible for a 7-digit number? How many people in a population can exist without having to exceed the seven digit combinations and having to revert to a 8 or 9 digit number?

Thanks and Many Blessings,



Hi Ky,

Is 0004764 a 7-digit number or does the leftmost digit have to be non-zero? What about 0000000?

If you are counting people in population you probably want the numbers

1 (that is 0000001); 2; 3; ...; 9999999

and there are 9,999,999 such numbers.

If you are thinking of something like telephone numbers where the first digit can't be zero then, from the list above you have to eliminate the 999,999 numbers

1; 2; 3;...; 999999

In this case there are then

9,999,999 - 999,999 = 9,000,000



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