Question

a bag contains five red cubes and seven white cubes. celinda will select one cube, put it in her pocket and select a second cube. Which expression given the probability she will select two red cubes?

Answer 1

Sample space ={R,R,R,R,R,W,W,W,W,W,W,W} = (5 R + 7 W = 12)

1st selection: P(one red) = 5/12 = 0.4167. Now the remaining cubes after the 1st selection : 4 Red and 7 Whites = 11 cubes), so 

2nd .selection P(one red) = 4/11 = 0.3667

This is a conditional probability and the condition is ; GET 2 REDS.
Hence P(getting one red AND getting also a red) = 5/12 x 4/11 =20/132=5/33 or 0.15

Answer 2

 probability of picking up 2 red cubes = 5/12 * 4/11 = 20/121. 

20 / 121 = .165 or .17

So the probability of Celinda getting two red cubes is .17.

I hope this helps!