The number of ways in which 3 numbers can be selected from first 45 natural numbers such that they are in arithmetic progression, is :

The number of ways in which four letters can be selected from the word degree, is

The number of ways in which four letters can be selected from the word degree, is

Number of ways in which three numbers in AP can be selected from 1,2,3, . .,n is

Number of ways in which three numbers in AP can be selected from 1,2,3, . .,n is

Number of ways in which three numbers in A.P. can be selected from 1,2,3,..., n is

The number of ways of selecting two distinct numbers from the first 15 natural numbers such that their sum is a multiple of 5, is equal to

The number of ways of selecting two distinct numbers from the first 15 natural numbers such that their sum is a multiple of 5, is equal to

Two numbers are selected from first 40 natural numbers. The probability that the sum of two number is odd is: