In how many different ways can the first 12 natural numbers be divided into three different groups such that numbers in each group are in A.P.? a. `1` b. `5` c. `6` d. `4`

The number of different ways in which the first twelve natural numbers can be divided into three groups, each having four elements, such that the numbers in each group are in arithmetic progression is

In how many different ways can the letters of the word 'NUMBER' be arranged?

The number of ways in which 12 students can be equally divided into three groups is

The number of ways can five people be divided into three groups is