Question

A credit card contains 16 digits between 0 and 9. However, only 300 million numbers are valid. If a number is entered randomly, what is the probability that it is a valid number

Answer 1

The probability that a randomly entered number is valid will be 0.00000003

Explanation

From 0 to 9, there are total 10 digits and the credit card number should be of 16 digits.

So, the total possible 16 digit credit card numbers $=10^1^6$

Now, the valid numbers are only 300 millions $i.e$ $3*10^8$

Thus, the probability that a randomly entered number is valid $= \frac{3*10^8}{10^1^6}= 3*10^-^8 = 0.00000003$