If `n_1` and `n_2` are five-digit numbers, find the total number of ways of forming `n_1` and `n_2` so that these numbers can be added without carrying at any stage.

n_(1) and n_(2) are four-digit numbers,find the total number of ways of forming n_(1) and n_(2) so that n_(2) can be subtracted from n_(1) without borrowing at any stage.

Find the total number of n -digit number (n>1) having property that no two consecutive digits are same.

Given that n is odd, number of ways in which three numbers in AP can be selected from 1, 2, 3,……., n, is

Find the total number of integer n such that 2<=n<=2000 and H.C.F.of n and 36 is 1.

There are n numbered seats around a round table. Total number of ways in which n_(1)(n_(1) lt n) persons can sit around the round table, is equal to