Maximum Value of nCr

Q.

In how many ways can $6$ persons be selected from $4$ officers and $8$ constables, if at least one officer is to be?

1. $224$

2. $672$

3. $896$

4. None of these

Q.

A person wishes to make up as many different parties as he can out of 20 friends with the condition that each party consists of the same number. How many should he invite at a time?

1. 5
   

2. 10
   

3. 20

4. 15
   

Q.

A person wishes to make up as many different parties as he can out of 20 friends with the condition that each party consists of the same number. How many should he invite at a time?

1. 5
   

2. 10
   

3. 15
   

4. 20