Question

Mrs. Gomes found that 40% of students at her high school take chemistry. She randomly surveys 12 students. What is the probability that exactly 4 students have taken chemistry? Round the answer to the nearest thousandth. A)0.005 B)0.008 C)0.213 D)0.227

Answer 1

Binomial formula is :
$P ( k = 4 ) = nCk * p ^{k}(1-p) ^{n}= \\ =495 * 0.4 ^{4}* ( 0.6 ) ^{8}=$
= 495 * 0.0256 * 0.0167961 =
= 0.21284 ≈ 0.213
Answer: C ) 0.213

Answer 2

Answer:

The correct option is C. 0.213

Step-by-step explanation:

Percentage of students at high school who takes chemistry = 40%

So, probability of students who take chemistry = 0.4

So, probability of students who do not take chemistry = 1 - 0.4

                                                                                          = 0.6

Total number of students taken for survey = 12

Now, we need to find the probability that exactly 4 students have taken chemistry among the 12 surveyed students.

By using binomial distribution :

n = 12 , p = 0.4 , q = 0.6 , k = 4

$\text{Required Probability = }_{k}^{n}\textrm{C}\cdot(p)^k\cdot(q)^{n-k}\\\\\implies\text{Required Probability = }_{4}^{12}\textrm{C} \cdot(0.4)^4 \cdot(0.6)^8 \\\\\implies \text{Required Probability = }0.2128\approx 0.213$

Therefore, The correct option is C. 0.213