Answer:
Explanation:
To check whether the given credit card number is valid or not, we need to apply the Luhn algorithm or the mod-10 algorithm. The Luhn algorithm works by adding up all the digits in the credit card number and checking if the sum is divisible by 10 or not. If it is, then the credit card number is considered valid, otherwise, it is invalid.
Let's apply the Luhn algorithm to the given credit card number:
Step 1: Starting from the rightmost digit, double every second digit
| 5 | 4 | 2 | 4 | 9 | 8 | 1 | 3 | 2 | 7 | 2 | 0 | 0 | 0 | 8 | 5 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| | 8 | | 8 | | 16| | 6 | | 14| | 0 | | 0 | | 10|
Step 2: If the doubled value is greater than 9, add the digits of the result
| 5 | 4 | 2 | 4 | 9 | 8 | 1 | 3 | 2 | 7 | 2 | 0 | 0 | 0 | 8 | 5 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| | 8 | | 8 | | 7 | | 6 | | 5 | | 0 | | 0 | | 1 |
Step 3: Add up all the digits in the credit card number, including the check digit
5 + 4 + 2 + 4 + 9 + 8 + 1 + 3 + 2 + 7 + 2 + 0 + 0 + 0 + 8 + 5 + 1 = 61
Step 4: If the sum is divisible by 10, then the credit card number is valid, otherwise, it is invalid.
61 is not divisible by 10, therefore the given credit card number is invalid.
Hence, it can be concluded that 5424 9813 2720 0085 is an invalid MASTERCARD credit card number.