Question

Supposed a Visa card had a credit card number of 4162 0012 3456789a where a is the check number what is the check number? A) 0 B) 3 C) 9 D) 7

Answer 1

Option B) 3

Explanation:

we have the number

4162 0012 3456 789a

Find the value of a (check number)

step 1

Multiply every even-position digit (when counted from the right) in the number by two. If the result is a two digit number, then add these digits together to make a single digit

4162 0012 3456 789a

9(2)+7(2)+5(2)+3(2)+1(2)+0(2)+6(2)+4(2)

(18)+(14)+(10)+(6)+(2)+(0)+(12)+(8)

Remember that If the result is a two digit number, then add these digits together to make a single digit

so

(1+8)+(1+4)+(1+0)+(6)+(2)+(0)+(1+2)+(8)

(9)+(5)+(1)+(6)+(2)+(0)+(3)+(8)=34

step 2

add every odd-position digit

4162 00123456 789a

so

8+6+4+2+0+2+1=23

step 3

Adds the result in step 1 and the result in step 2

34+23=57

The check-digit is what number needs to be added to this total to make the next multiple of 10

In our case, we’d need to add 3 to make 60

therefore

The check number is 3