1
IIT-JEE 2006
MCQ (Single Correct Answer)
+3
-1

There are $$n$$ urns each containing $$n+1$$ balls such that the $$i^{\text {th }}$$ urn contains $$i$$ white balls and $$(n+1-i)$$ red balls. Let $$u_{i}$$ be the event of selecting $$i^{\text {th }}$$ urn, $$i =1,2,3 \ldots, n$$ and $$w$$ denotes the event of getting a white ball.

If $$\mathrm{P}\left(u_{i}\right)=c$$, where $$c$$ is a constant then $$\mathrm{P}\left(u_{n} / w\right)$$ is equal to:

A
$$\frac{2}{n+1}$$
B
$$\frac{1}{n+1}$$
C
$$\frac{n}{n+1}$$
D
$$\frac{1}{2}$$
2
IIT-JEE 2006
MCQ (Single Correct Answer)
+3
-1

There are $$n$$ urns each containing $$n+1$$ balls such that the $$i^{\text {th }}$$ urn contains $$i$$ white balls and $$(n+1-i)$$ red balls. Let $$u_{i}$$ be the event of selecting $$i^{\text {th }}$$ urn, $$i =1,2,3 \ldots, n$$ and $$w$$ denotes the event of getting a white ball.

If $$n$$ is even and E denotes the event of choosing even numbered urn $$\left(\mathrm{P}\left(u_{i}\right)=\frac{1}{n}\right)$$, then the value of $$\mathrm{P}(w / \mathrm{E})$$ is :

A
$$\frac{n+2}{2 n+1}$$
B
$$\frac{n+2}{2(n+1)}$$
C
$$\frac{n}{n+1}$$
D
$$\frac{1}{n+1}$$
3
IIT-JEE 2005 Screening
MCQ (Single Correct Answer)
+2
-0.5
A six faced fair dice is thrown until $$1$$ comes, then the probability that $$1$$ comes in even no. of trials is
A
$$5/11$$
B
$$5/6$$
C
$$6/11$$
D
$$1/6$$
4
IIT-JEE 2005 Mains
MCQ (Single Correct Answer)
+3
-1

A person goes office either by car, scooter, bus or train, proability of which being $$\frac{1}{7}, \frac{3}{2}, \frac{2}{7}$$ and $$\frac{1}{7}$$, respectively. Probability that he reaches office late, if he takes car, scooter, bus or train is $$\frac{2}{9}, \frac{1}{9}, \frac{4}{9}$$ and $$\frac{1}{9}$$, respectively. Given that he reached office in time, then what is the probability that he travelled by a car?

A
$$\frac{1}{7}$$
B
$$\frac{1}{8}$$
C
$$\frac{3}{7}$$
D
$$\frac{3}{8}$$

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