Question

The chance of a student passing an exam is 20%. The chance of student passing the exam and getting above 90% marks in it is 5%. Give 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 passing the exam}
B = {Getting above 90% marks}

$\text{So, Required Probability is}$
$P\left(A/B\right)=\frac{P(B\cap A)}{P\left(A\right)}=\frac{0.05}{0.2}=\frac{1}{4}$