Question

In four schools $\text{B1, B2, B3, B4}$ the percentage of girls students is $12,20,13,17$ respectively.

From a school selected at random, one student is picked up at random and it is found that the student is a girl.

The probability that the school selected is $\text{B2}$ is

• A. $\frac{6}{31}$
• B. $\frac{10}{31}$
• C. $\frac{13}{62}$
• D. $\frac{17}{62}$

Answer 1

The correct option is B

$\frac{10}{31}$

Explanation for correct answer Option(s)

Find the probability of the girl selected from $\text{B2}$.

The total number of ways, for a girl to be selected can be expressed as, $12+20+13+17=62$

Number of ways of selecting a girl from school $\text{B2=}{}^{20}{\mathbb{\text{ℂ}}}_1$

Therefore, The probability of the girl selected from $\text{B2}$ can be expressed as,

$$\begin{gathered} \text{P(B2)}=\frac{{}^{20}{C}_1}{62} \\ =\frac{20}{62} \\ =\frac{10}{31} \end{gathered}$$

Therefore, the correct answer is Option (B).