Question

A bag contains one red pen, four black pens, and three blue pens. Two pens are randomly chosen from the bag and are not

replaced.
To the nearest hundredth, what is the probability that a black pen is chosen first and then another black pen is chosen?
0.02
0.19
0.21
0.25

Answer 1

.21

Explanation:

Answer 2

Answer: 0.21

Explanation:

Given : A bag contains one red pen, four black pens, and three blue pens.

Total pens = 1+4+3=8

Probability that first pen was black =
`\frac{\text{Number of black pens}}{\text{Total pens}}=(4)/(8)=0.5`

Probability that the next second pen was black given that the first was black =
`\frac{\text{Number of black pens left}}{\text{Total pens left}}=(3)/(7)`

Using conditional probability formula , the probability that a black pen is chosen first and then another black pen is chosen = (Probability that first pen was black) x (Probability that the next second pen was black given that the first was black)

=
`0.5*(3)/(7)=0.214285714286\apptox0.21`

Hence, the correct answer is 0.21.