A quality control inspector...

Question

A quality control inspector samples 6 computer chips from a box containing 12 computer chips. If the box contains 2 defective chips. In how many ways can he select a sample so that both defective chips are selected?

Answer 1

We have 6 selection locations:

 

__ __ __ __ __ __

 

From these locations, two are predetermined and 10 remain in the box:

 

A B __ __ __ __

 

Thus, there are 10 chips available and we are selecting 4, so we have:

(10C4) combinations which include the two defective chips.