Question

A bag contains 4 red balls and 5 black balls. In how many ways can i make a selection so as to take at least 1 red ball and 1 black ball

Answer 1

take out one ball from both bags

Answer 2

We have 4 red balls and 5 black balls we need to have atleast 1 ball from each of them

So

(2^4 -1)*(2^5-1) =465

where -1 in each of them indicates that we are taking out chances of haveing 0 ball