In a bank, it doesn't issue the PIN code with more than 2 consecutive digits the same.(For example, 7666 and 2222 are not allow but 0040 is allowed)
i)how many different PIN codes are possible?
ii)how many different PIN codes have 8 as their first digits?
I don't really know how to solve this question, is there a easy way to solve it? can anyone helped me?Thank you very much!!