A credit card number has 6 digits (between 1 to 9 inclusive). The first two digits are 12 in that order, the third digit is bigger than 6, the fourth digit is divisible by 3, and the fifth digit is 4 times the sixth. How many different credit card numbers are possible?
Choices.
A) 12
B) 15
C) 18
D) 24
E) 36
The first two digits are fixed.   The third digit can be 7, 8, or 9 so there are 3 choices.   The fourth digit can be 3, 6, or 9 so there are 3 choices.   The fifth digit depends entirely on the sixth digit.   The sixth digit can be 1 or 2 so there are 2 choices.   The number of possibilities is  3*3*2= 
<gadget id="calculator"> 3*3*2</gadget>
<output>18</output>
18   The answer is 18.
<result>C</result>
A credit card number has 6 digits (between 1 to 9 inclusive). The first two digits are 12 in that order, the third digit is bigger than 6, the fourth digit is divisible by 3, and the fifth digit is 4 times the sixth. How many different credit card numbers are possible?