Advertisements
Advertisements
प्रश्न
Select the correct option from the given alternatives :
The probability that a student knows the correct answer to a multiple choice question is `2/3`. If the student does not know the answer, then the student guesses the answer. The probability of the guessed answer being correct is `1/4`. Given that the student has answered the question correctly, the probability that the student knows the correct answer is
पर्याय
`5/6`
`6/7`
`7/8`
`8/9`
उत्तर
`8/9`
Explanation:
Let event A: Student knows the correct answer.
event A': Student guesses the answer.
event B: Answer is correct
∴ P(A) = `2/3`, P(A') = `1/3, "P"("B"/"A'") = 1/4`
Clearly, `"P"("B"/"A")` = 1
Required probability = `"P"("A"/"B")`
= `("P"("A")*"P"("B"/"A"))/("P"("A")*"P"("B"/"A") + "P"("A'")"P"("B"/"A'"))`
= `(2/3 xx 1)/(2/3 xx 1 + 1/3 xx 1/4)`
= `8/9`
APPEARS IN
संबंधित प्रश्न
A fair die is thrown two times. Find the probability that the first throw gives a multiple of 2 and the second throw gives a multiple of 3.
A fair die is thrown two times. Find the probability that the product of numbers on them is 12.
Two cards are drawn from a pack of 52 cards. Find the probability that one is club and the other is a diamond.
Two cards are drawn from a pack of 52 cards. Find the probability that both are red cards
Three cards are drawn from a pack of 52 cards. Find the chance that at least one is a diamond card
Three cards are drawn from a pack of 52 cards. Find the chance that they are a king, a queen, and a jack
Find the probability of getting both red balls, when from a bag containing 5 red and 4 black balls, two balls are drawn, without replacement
Letters of the word MOTHER are arranged at random. Find the probability that in the arrangement vowels are always together.
Letters of the word MOTHER are arranged at random. Find the probability that in the arrangement O is at the begining and end with T
15 professors have been invited for a round table conference by Vice chancellor of a university. What is the probability that two particular professors occupy the seats on either side of the Vice chancellor during the conference
A bag contains 7 black and 4 red balls. If 3 balls are drawn at random find the probability that one is black and two are red.
A bag contains 75 tickets numbered from 1 to 75. One ticket is drawn at random. Find the probability that, number on the ticket is a prime number or greater than 40
A bag contains 5 red, 4 blue and an unknown number m of green balls. If the probability of getting both the balls green, when two balls are selected at random is `1/7`, find m
Form a group of 4 men, 4 women and 3 children, 4 persons are selected at random. Find the probability that, no child is selected.
Select the correct option from the given alternatives :
There are 5 girls and 2 boys, then the probability that no two boys are sitting together for a photograph is
Select the correct option from the given alternatives :
Two dice are thrown simultaneously. Then the probability of getting two numbers whose product is even is
Select the correct option from the given alternatives :
Two friends A and B apply for a job in the same company. The chances of A getting selected is `2/5` and that of B is `4/7`. The probability that both of them get selected is
Solve the following:
A die is loaded in such a way that the probability of the face with j dots turning up is proportional to j for j = 1, 2, .......6. What is the probability, in one roll of the die, that an odd number of dots will turn up?
Ram is visiting a friend. Ram knows that his friend has 2 children and 1 of them is a boy. Assuming that a child is equally likely to be a boy or a girl, then the probability that the other child is a girl, is ______.
A coin is tossed 9 times. The probability of obtaining at most one head is ______
If three dices are thrown then the probability that the sum of the numbers on their uppermost faces to be atleast 5 is ______.
The probability that three cards drawn from a pack of 52 cards, all are red is ______.
A coin is tossed 2n times. The chance that the number of times one gets head is not equal to the number of times one gets tail is ______.
Four mangoes and five apples are in a box. If two fruits are chosen at random, then find the probability that one is a mango and other is an apple ______.
If two letters of the word MOTHER are selected at random. Probability that both are consonants is ______.
A die is thrown four times. The probability of getting perfect square in at least one throw is ______.
Probability that a person will develop immunity after vaccinations is 0.8. if 8 people are given the vaccine, then probability that all develop immunity is = ______.
If 15 coupons are numbered 1, 2, 3, ..., 15, respectively. 7 coupons are selected at random one at a time with replacement. The probability that the largest number appearing on a selected coupon is almost 9, is ______.
The probability of India winning a test match against South Africa is 1/2 assuming independence form match to match played. The probability that in a match series India's second win occurs at the third day is ______.
