Home
Class 12
MATHS
In an examination, 20 questions of true-...

In an examination, 20 questions of true-false type are asked. Suppose a student tosses a fair coin to determine his answer to each question. If the coin falls heads, he answers 'true', if it falls tails, he answers 'false'. Find the probability that he answers at least 12 questions correctly.

Text Solution

Verified by Experts

The correct Answer is:
`((1)/(2))^(20)[20C_(12)+""^(20)C_(13)+...+""^(20)C_(20)]`
Promotional Banner

Topper's Solved these Questions

  • PROBABILITY

    NCERT BANGLISH|Exercise MISCELLANEOUS EXERCISE ON CHAPTER 13|19 Videos

  • PROBABILITY

    NCERT BANGLISH|Exercise EXERCISE 3.4|17 Videos

  • MATRICES

    NCERT BANGLISH|Exercise Miscellaneous Exercise on Chapter 3|15 Videos

  • RELATIONS AND FUNCTIONS

    NCERT BANGLISH|Exercise MISCLELLANEOUS EXERCISE ON CHAPTER 1|19 Videos

Similar Questions

Explore conceptually related problems

In an entrance test, there are multiple choice questions. There are four possible answers to each question, of which one is correct. The probability that a student knows the answer to a question is 90%. If the gets the correct answer to a question, then find the probability that he was guessing.

Let's find total marks obtained by sayan if he answered 6 question correctly and 6 questions answered incorrectly.

In a test an examine either guesses or copies or knows the answer to a multiple choice question with four choices. The probability that he makes a guess is 1/3 and the probability that the copies the answer is 1/6. The probability that his answer is correct, given that he copied it, is 1/8. Find the probability that he knew the answer to the question, given that he correctly answered it.

answer any one question : 2.eight unbiased coins tossed . Find the probability of getting exactly five heads

answer any one question : (ii) an unbiased coin is tossed 6 times . Using binomial distribution , find the probability of getting at least 5 heads.

In a multiple choice question, there are four alternative answers of which one or more than one is correct A candidate will get marks on the question only if he ticks the correct answer. The candidate decides to tick answers at a random. If he is allowed up to three chances to answer the question, then find the probability that he will get marks on it.

In answering a question on a multiple choice test, a student either knows the answer or guesses. Let (3)/(4) be the probability that he knows the answer and (1)/(4) be the probability that he guesses. Assuming that a student who guesses at the answer will be correct with probability (1)/(4) . What is the probability that the student knows the answer given that he answered it correctly?

On a multiple choice examination with 4 possible answers for each of 6 questions the probability that a student would get at least two correct answers just by guessing is -

An objective type test paper has 5 questions. Out of these 5 questions, 3 questions have four options eah (A,B,C,D) with one option being the correct answer. The other 2 questions have two options each, namely True and False. A candidate randomly ticks the options. Then the probability that he/she will tick the correct option in at least four question is-

A multiple choice emamination has 5 questions. Each question has three alternative answers of which exactly one is correct. The probability that a student will get 4 or more correct answers just guessing is