How do get the answer to this probability problem? Do you use the nCr or nPr formula? If so how?

A televisions/stereo store has 12 different plasma televisions and 8 different LCD televisions in stock. The store's manager wishes to place 3 plasma televisions and 2 LCD televisions on sale. In how many ways can that be done?How do get the answer to this probability problem? Do you use the nCr or nPr formula? If so how?
Do step by step, i will chose 3 plasma televisions first, then i chose 2 LCD televisions ,ok?


Chose 3 plasma televisions from 12 (no order) We have 12C3 ways to do it.


Chose 2 LCD televisions from 8( no order) We have 8C2 ways to do it.


Now multiple them together (mn counting rule)


We have 12C3*8C2 ways to chose 5 televisions that satisfy your question, right?


To chose 5 televisions from 12 plasma televisions and 8 LCD televisions, we have (12+8)C5=20C5 ways to do it.


So the probability would be (12C3*8C2)/20C5


Hope it helpsHow do get the answer to this probability problem? Do you use the nCr or nPr formula? If so how?
Putting them on sale doesn't mind about what order you put the TVs/Stereos in, so you'd use nCr.





The answer would be 12C3 x 8C2





220 x 28 = 6,160 ways.