Permutations and Combinations.

In some questions (like the one given below) we come across a dilemma to either to add or to multiply. Please tell me how do you do these type questions?

Ex--

4 cards are chosen from a pack of 52 cards.In how many of these --

a)Four cards are of same suit

b)two are red cards and two are black cards.

In case (a) we add but in case (b) we multiply.Why?

Thanks

Nitin Gupta

15 Years agoGrade 11