SOLUTION: A credit card number has 16 digits between 0 and 9 inclusive.If only 100 million numbers are valid, what is the probability that a number that is entered ramdomly is valid?

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Question 1099807: A credit card number has 16 digits between 0 and 9 inclusive.If only 100 million numbers are valid, what is the probability that a number that is entered ramdomly is valid?
Found 2 solutions by Edwin McCravy, Alan3354:
Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!
The smallest credit card number is 
 0000000000000000 and the largest is 

 9999999999999999.  From 1 to 
 9999999999999999 is 
 9999999999999999 numbers and 
 0000000000000000 makes it
10000000000000000

100 million valid numbers is 
100000000 so the probability is
100000000/10000000000000000 which reduces to

1/100000000

Edwin
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
A credit card number has 16 digits between 0 and 9 inclusive.If only 100 million numbers are valid, what is the probability that a number that is entered ramdomly is valid?
-------------
Assuming leading zeroes are allowed, ie, 0000000000000001 is used:
1e8/1e16 = 1e-8
--> 0.00000001
-------------
If leading zeroes not allowed:
--> 1e8/9e15
= 1/(9e7)

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