longhaul123 wrote:
I have a doubt on this question. It says between 1 to 9 so do we have to consider 1 and 9 because it thought we have to consider only 2,3,4,5,6,7,8 as the total number available. so the 3rd place can be filled with 2 ways (7 or 8) then the 4th place can be filled with 2 ways (3 or 6). I am not understanding how to fill the 5th and the 6th place because if you consider any value for the 6th place you get a 2 digit number for the 5th place right?? Am i wrong in my steps?? Kindly help
Between 1 and 9(include 1 and 9 in this case)
Now, considering that information,
The third digit is 7,8 or 9.(3 combinations)
Fourth digit which is divisible by 3, has to be 3,6, or 9(3 combinations)
Coming to the fifth and sixth digits,
Since fifth digit's value is thrice sixth's digit value
Again there are 3 combinations for the combination of fifth and sixth digits
5th Digit ---- 6th digit
----3---------------1-----
----6---------------2-----
----9---------------3-----
They are 3 combinations possible for the combination
All in all, the total ways the credit card could be formed are 3*3*3 = 27 ways(Option A)
Hope that helps!
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