Question

The chance of a student passing an exam is 20%. The chance of a student passing the exam and getting above 90% in it is 5%. Given that a student passes the examination, the probability that the student gets above 90% marks is

• A. $\frac{1}{18}$
• B. $\frac{1}{4}$
• C. $\frac{2}{9}$
• D. $\frac{5}{18}$

Answer 1

The correct option is B $\frac{1}{4}$

Let
A : Student getting above 90% Marks
B : Student passes exam.

$\therefore P\left(A/B\right)=\frac{P(A\cap B)}{P\left(B\right)}$

$=\frac{P\left(studentpassesandgettingabove90\%\right)}{P_{(}studentpassesexam)}$

$=\frac{0.05}{0.2}=\frac{1}{4}$