If all the possible 3-digit numbers are formed using the digits $1,3,5,7$ and 9 without repeating any digit, then the number of such 3 -digit numbers which are divisible by 3 is

A question paper has 3 parts $A, B$ and $C$. Part $A$ contains 7 questions, part $B$ contains 5 questions and Part Ccontains 3 questions. If a candidate is allowed to answer not more than 4 questions from part $A$; not more than 3 questions from part $B$ and not more than 2 questions from part $C$, then the number of ways in which a candidate can answer exactly 7 questions is

Among the 4 -digit numbers that can be formed using the digits $1,2,3,4,5$ and 6 without repeating any digit, the number of numbers which are divisible by 6 is

If the number of circular permutations of 9 distinct things taken 5 at a time is $n_1$ and the number of linear permutation of 8 distinct things taken 4 at a time is $n_2$, then $\frac{n_1}{n_2}=$