Advertisements
Advertisements
Question
There are 1000 students in a school out of which 450 are girls. It is known that out of 450, 20% of the girls studying in class XI. A student is randomly selected from 1000 students. What is the probability that the selected student is from class XI given that the selected student is a girl?
Solution
Number of students = 1000 i.e., n(S) = 1000
Let A be the event of selecting a girl student from class XI.
Let B be the event of selecting a girl student
Number of girls = 450
n(B) = 450
∴ P(B) = `("n"("B"))/("n"("S")) = 450/1000`
Number of girls studying in XI is 20% of 450 = `20/100 xx 450` = 90
i.e., n(A ∩ B) = 90
∴ P(A ∩ B) = `("n"("A" ∩ "B"))/("n"("S")) = 90/100`
We have to find P`("A"/"B")`
`"P"("A"/"B") = ("P"("A" ∩ "B"))/("P"("B")) = (90/1000)/(450/1000) = 90/450 = 1/5 = 0.2`
APPEARS IN
RELATED QUESTIONS
A family has two children. What is the probability that both the children are girls given that at least one of them is a girl?
The first of three urns contains 7 White and 10 Black balls, the second contains 5 White and 12 Black balls and the third contains 17 White balls and no Black ball. A person chooses an urn at random and draws a ball from it. And the ball is found to be White. Find the probabilities that the ball comes from
- the first urn
- the second urn
- the third urn
A card is drawn from a pack of playing cards and then another card is drawn without the first being replaced. What is the probability of drawing
- two aces
- two spades
A company has three machines A, B, C which produces 20%, 30% and 50% of the product respectively. Their respective defective percentages are 7, 3 and 5. From these products, one is chosen and inspected. If it is defective what is the probability that it has been made by machine C?
The probability of drawing a spade from a pack of card is
If the outcome of one event does not influence another event then the two events are
Probability of an impossible event is _________.
An experiment has the four possible mutually exclusive and exhaustive outcomes A, B, C, and D. Check whether the following assignments of probability are permissible.
P(A) = 0.15, P(B) = 0.30, P(C) = 0.43, P(D)= 0.12
Eight coins are tossed once, find the probability of getting atleast two tails
Choose the correct alternative:
A bag contains 6 green, 2 white, and 7 black balls. If two balls are drawn simultaneously, then the probability that both are different colours is
