ISRO CS 2017 – May

Question 1

If A is a skew symmetric matrix, then A^t

• A. diagonal matrix
• B. A
• C. -A
• D. 0

Answer: (C)

If A is skew symmetric matrix then A^T = -A

Question 2

If A and B be two arbitrary events, then

• A. P(A ∩ B) = P(A)P(B)
• B. P(A ∪ B) = P(A) + P(B)
• C. P(A / B) = P(A ∩ B) + P(B)
• D. P(A ∪ B) <= P(A) + P(B)

Answer: (D)

Case:1 P(A ∪ B) = P(A) + P(B) - P (A ∩ B). Case:2 For two mutually exclusive events, (A ∩ B) = 0, So P(A ∪ B) <= P(A) + P(B) So, option (D) is correct.

Question 3

Using Newton-Raphson method, a root correct to 3 decimal places of the equation x³ - 3x - 5 = 0

• A. 2.222
• B. 2.275
• C. 2.279
• D. None of the above

Answer: (C)

Question 4

What does the data dictionary identify?

• A. Field names
• B. Field formats
• C. Field Types
• D. All of these

Answer: (D)

Question 5

Which of the following concurrency control protocol ensures both conflict serializability and free from deadlock?

• A. Time stamp ordering
• B. 2 Phase locking
• C. Both (a) and (b)
• D. None of the above

Answer: (A)

Both Time stamp ordering and 2 Phase locking protocol ensures conflict serializability but only Time stamp ordering protocol provides freedom from deadlock.

Question 6

ACID properties of a transactions are

• A. Atomicity, consistency, isolation, database
• B. Atomicity, consistency, isolation, durability
• C. Atomicity, consistency, integrity, durability
• D. Atomicity, consistency, integrity, database

Answer: (B)

Every transaction holds ACID properties. A: Atomicity: Either a transaction should be performed completely or it should rollback. C: Consistency: Every transaction specifies some consistency constraints and these constraints should follow even after transaction occurs. I: Isolation: Every transaction should be performed in isolation so that no other transaction can see the intermediate result of any transaction. D: Durability: Every transaction performed should be recorded and despite all the failures these records must persist.

Question 7

What is the output of the following SQL query?

select count(*) from ((select Employee, Department from Overtime_allowance) as S
natural join (select Department, OT_allowance from Overtime_allowance) as T);

• A. 16
• B. 4
• C. 8
• D. None of the above
• E. none

Answer: (B)

(select Employee, Department from Overtime_allowance) as S natural join (select Department, OT_allowance from Overtime_allowance) as T)

Table S                          Table R
Employee     Department          Department     OT_allowance
Rama         Mechanical          Mechanical     5000
Gopi         Electrical          Electrical     2000
Sindhu       Computer            Computer       4000
Mahesh       Civil               Civil          1500

Now when we apply a natural join on S and R, it matches the common attribute Department in both the tables and outputs the common tuples. So, 4 tuples will be given as the output. Correct option (B)

Question 8

Which symbol denote derived attributes in ER Model?

• A. Double ellipse
• B. Dashed ellipse
• C. Squared ellipse
• D. Ellipse with attribute name underlined

Answer: (B)

Refer:Database Management System | ER Model Correct option (B)

Question 9

The symmetric difference of sets A = {1, 2, 3, 4, 5, 6, 7, 8} and B = {1, 3, 5, 6, 7, 8, 9} is

• A. {1, 3, 5, 6, 7, 8}
• B. {2, 4, 9}
• C. {2, 4}
• D. {1, 2, 3, 4, 5, 6, 7, 8, 9}

Answer: (B)

Symmetrical Difference of A and B

= (A – B) ∪ (B – A)

(A – B) = {2, 4}
(B – A) = {9}

(A – B) ∪ (B – A) = {2, 4} ∪ {9} = {2, 4, 9} 

Question 10

The problems 3-SAT and 2-SAT are

• A. Both NP-complete
• B. Both in P
• C. NP-complete and in P, respectively
• D. Undecidable and NP-complete, respectively

Answer: (C)

3-SAT problem is NP- complete problem whereas 2- SAT problem is P- class problem. Refer: 2-Satisfiability (2-SAT) Problem Option (C) is correct.