AP EAMCET201823 Apr 2018Evening ShiftMathematicsProbabilityActual
In a certain recruitment test with multiple choice questions, there are four options to answer each question, out of which only one is correct. An intelligent student knows 90 % correct answers while a weak student known only 20 % correct answers. If an intelligent student gets the correct answer for a question, then the probability that he was guessing it, is
Options
- A1 37
- B1 10
- C9 37
- D1 2
Correct answer
A. 1 37
Step-by-step solution
Let the events E₁= he guesses the answer E₂= he knows the answer A= he answers correctly Then, aligned P (E₂ ) & = 9 10 , & P (E₁ ) & = 1 10 P (A E₂ ) & =1, & P (A E₁ ) & = 1 4 aligned So, aligned P (E₁ A ) & = P (E₁ ) P (A E₁ ) P (E₁ ) P (A E₁ )+P (E₂ ) P (A E₂ ) & = 1 10 1 4 ( 1 10 1 4 )+ ( 9 10 1 ) = 1 1+36 = 1 37 aligned