There are 20 multiple-choice questions on an exam, each having responses a, b, c, or d. Each question is worth 5 points, and only one response per question is correct. Suppose a student guesses the answer to each question, and her guesses from question to question are independent. If the student needs at least 40 points to pass the test, the probability the student passes is closest to
Accepted Solution
A:
Ok, the student needs 40 points and each question is worth 5, so 40/5 = 8 questions are needed. Each question has 4 possibilities, 1 is right, so the chances to guess it correctly is one in 4, or 1/4, or 25%.[tex]\frac{8}{20} = \frac{2}{5}[/tex]To know the probability to pass the exam we can do:[tex]\frac{25}{100}*\frac{2}{5} = 10%[/tex]