Given that the student studies Physics, what…

Given that the student studies Physics, what is the probability that the student is a girl?

Question 10

EasyOriginal question

A group of 60 students has 36 girls and 24 boys. Of the girls, 20 study Physics; of the boys, 8 study Physics. One student is picked at random from the group.

Given that the student studies Physics, what is the probability that the student is a girl?

\frac{1}{3}

Correct answerYour answer

\frac{5}{9}

Correct answerYour answer

\frac{3}{5}

Correct answerYour answer

\frac{5}{7}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer D

Correct answer: D

Physics students: $20 + 8 = 28$ .
20 of them are girls: $\frac{20}{28} = \frac{5}{7}$ .

Worth noting

$\frac{5}{9}$ is the chance that a girl studies Physics, the condition the other way round.

Concept: Conditional probability by counting
Typical timeTypical: 90 s
Your timeYours: —

The rule this testsConditional probability

Practise this chapter →

Ten questions from Conditional Probability & Bayes' Theorem, at your own pace.

Practise this chapter →

Ten questions from Conditional Probability & Bayes' Theorem, at your own pace.

Given that the student studies Physics, what is the probability that the student is a girl?

Question 10

Explanation