Math, asked by mehartanveer029, 11 months ago

In a multiple-choice quiz, there are 5 questions and 4 choices for each question (a, b, c, d). Robin has
not studied for the quiz at all, and decides to randomly guess the answers. What is the probability that:
a. the first question she gets right is the 3rd question?
b. she gets exactly 3 or exactly 4 questions right?
c. she gets the majority of the questions right?

Answers

Answered by devanshii42
0

Answer:

option c is correct

hope it will help you

Answered by ParvezShere
0

a) probability that the first question she gets right is the 3rd question = 48/256

b) probability that she gets exactly 3 or exactly 4 questions right = 675/1024

c) probability that she gets the majority of the questions right = 918/1024

Probability of getting a question right = 1/4

Probability of getting a question wrong = 3/4

If she gets the first question right as the third question -

probability = (1/4 × 1/4 × 3/4 × 1/4 × 1/4) + (1/4 × 1/4 × 3/4 × 3/4 × 3/4) + (1/4 × 1/4 × 3/4 × 1/4 × 3/4) + (1/4 × 1/4 × 3/4 × 3/4 × 1/4)

=> 3/256 + 27/256 + 9/256 + 9/256

=> 48/256

If she gets exactly 3 or 4 questions right -

probability = 5C3 (3/4)³ (1/4)² + 5C4 (3/4)⁴ (1/4)

=> (10 × 27)/1024 + 405/1024

=> 675/1024

If she gets majority of the questions right -

probability = 5C3 (3/4)³ (1/4)² + 5C4 (3/4)⁴ (1/4) + 5C5 (3/4)^5

=> (10 × 27)/1024 + 405/1024 + 243/1024

=> 918/1024

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