From the set `{2, 3, 4, 5, 6, 7, 8, 9}`, how many pairs of co-primes can be formed?

The number of ways of selecting 4 numbers from the set S={1,2,3,4,5,6,7,8,9} such that they are not consecutive,is

How many three-digit number can be generated from 1, 2, 3, 4, 5, 6, 7, 8, 9, such that the digits are in ascending order?

How many numbers between 2000 and 3000 can be formed from the digits 2, 3, 4, 5, 6, 7 when repetition of digits is not allowed?

Let A={1,2,3,4,5,6,7,8,9). How many subsets does A have which contain 4,5 and 6?

Five different digits from the setoff numbers {1,2,3,4,5,6,7} are written in random order. How many numbers can be formed using 5 different digits from set {1,2,3,4,5,6,7} if the number is divisible by 9?