the number of ways in which 9 things can be divided into twice groups containing 2,3 and 4 things respectively is ?
Here , total number of things = 9,
So forming the first group by choosing 2 things out of 9 things that is, = 9C2
Now next group is formed by choosing 3 things out of 7 remaining things, that is, = 7C3
And next group is formed by choosing 4 things out of remaining 4 things, = 4C4
Hence the number of ways = 9C2 7C3 4C4 = 1260.
So forming the first group by choosing 2 things out of 9 things that is, = 9C2
Now next group is formed by choosing 3 things out of 7 remaining things, that is, = 7C3
And next group is formed by choosing 4 things out of remaining 4 things, = 4C4
Hence the number of ways = 9C2 7C3 4C4 = 1260.