NCERT Class 12-Mathematics: Chapter –13 Probability Part 10

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Question 30:

Two probability distributions of the discrete random variable X and Y are given below.

The discrete random variable X

The discrete random variable Y

Prove .

Answer:

The discrete random variable X

The discrete random variable Y

Since, we have to prove that,

From Eq. (i) and (ii),

Hence proved.

Question 31:

A factory produces bulbs. The probability that any one bulb is defective is and they are packed in boxes of 10. From a single box, find the probability that

(i) None of the bulbs is defective

(ii) Exactly two bulbs are defective

(iii) More than 8 bulbs work properly

Answer:

(i)

(ii)

(iii)

Question 32:

Suppose you have two coins which appear identical in your pocket. You know that one is fair and one is 2-headed. If you take one out, toss it and get a head, what is the probability that it was a fair coin?

Answer:

Let Event that a fair coin is drawn

Event that two headed coin is drawn

Event that tossed coin get a head

Now using Baye’s theorem

Question 33:

Suppose that of the people with blood group O are left handed and of those with other blood groups are left handed of the people have blood group O. If a left handed person is selected at random, what is the probability that he/she will have blood group O?

Answer:

The probability that he/she will have blood group O

Blood group ‘O’

Other than blood group ‘O’

I. Number of people

II. Percentage of left handed people

By using Baye’s theorem,

Question 34:

Two natural numbers are drawn one at a time, without replacement from the set . Find where.

Answer: