GATE CSE 2021 Set 2 | Probability Question 7 | Discrete Mathematics

GATE CSE 2021 Set 2

MCQ (Single Correct Answer)

-0.66

In an examination, a student can choose the order in which two questions (QuesA and QuesB) must be attempted.

- If the first question is answered wrong, the student gets zero marks.

- If the first question is answered correctly and the second question is not answered correctly, the student gets the marks only for the first question.

- If both the questions are answered correctly, the student gets the sum of the marks of the two questions.

The following table shows the probability of correctly answering a question and the marks of the question respectively.

question	Probability of answering correctly	marks
QuesA	0.8	10
QuesB	0.5	20

Assuming that the student always wants to maximize her expected marks in the examination, in which order should she attempt the questions and what is the expected marks for that order (assume that the questions are independent)?

First QuesB and then QuesA. Expected marks 14

First QuesB and then QuesA. Expected marks 22

First QuesA and then QuesB. Expected marks 14.

First QuesA and then QuesB. Expected marks 16.

GATE CSE 2021 Set 2

MCQ (Single Correct Answer)

-0.66

A bag has r red balls and b black balls. All balls are identical except for their colours. In a trial, a ball is randomly drawn from the bag, its colour is noted and the ball is placed back into the bag along with another ball of the same colour. Note that the number of balls in the bag will increase by one, after the trial. A sequence of four such trials is conducted. Which one of the following choices gives the probability of drawing a red ball in the fourth trial ?

$$\frac{r}{r+b}$$

$$\left(\frac{r}{r+b}\right)\left(\frac{r+1}{r+b+1}\right)\left(\frac{r+2}{r+b+2}\right)\left(\frac{r+3}{r+b+3}\right)$$

$$\left(\frac{r+3}{r+b+3}\right)$$

$$\left(\frac{r}{r+b+3}\right)$$

GATE CSE 2021 Set 1

MCQ (Single Correct Answer)

-0.67

Consider the two statements.

S₁ : There exist random variables X and Y such that

(E[X - E(X)) (Y - E(Y))])² > Var[X] Var[Y]

S₂ : For all random variables X and Y,

Cov[X, Y] = E [|X - E[X]| |Y - E[Y]|]

Which one of the following choices is correct?

S₁ is false, but S₂ is true.

S₁ is true, but S₂ is false.

Both S₁ and S₂ are true.

Both S₁ and S₂ are false.

GATE CSE 2021 Set 1

Numerical

-0

A sender (S) transmits a signal, which can be one of the two kinds: H and L with probabilities 0.1 and 0.9 respectively, to a receiver (R).

In the graph below, the weight of edge (u, v) is the probability of receiving v when u is transmitted, where u, v ∈ {H, L}. For example, the probability that the received signal is L given the transmitted signal was H, is 0.7.

GATE CSE 2021 Set 1 Discrete Mathematics - Probability Question 10 English
If the received signal is H, the probability that the transmitted signal was H (rounded to 2 decimal places) is ______