An eight-digit number is said to be 'robust' if it meets both of the following conditions:

(i) None of its digits is 0.
(ii) The difference between two consecutive digits is 4 or 5.

Answer the following questions:

(a) How many robust numbers are there?
(b) A robust number is said to be 'super robust' if all of its digits are distinct. Calculate the sum of all the super robust numbers.

Posted by K Sengupta on 2024-06-02 22:28:31