7,8,9
arguing about who has better teaching skills.
Problem 8.Your debit card pin now requires six digits.Solve that aHow many possible pins are there (b) Now the bank requires pins not to reuse digit. How many possible legit pins are there?
Problem 9.Without calculation,show that combination (s,a)equals combination (s,s-a)) using definition,where integers a,s satisfies s>1,a >0,s>=a.should be just one sentence)