# ISRO CS 2017 – May

• Last Updated : 22 Sep, 2021

 Question 1
If A is a skew symmetric matrix, then At
 diagonal matrix A -A 0

Question 1-Explanation:
If A is skew symmetric matrix then AT = -A
 Question 2
If A and B be two arbitrary events, then
 P(A ∩ B) = P(A)P(B) P(A ∪ B) = P(A) + P(B) P(A / B) = P(A ∩ B) + P(B) P(A ∪ B) <= P(A) + P(B)

Question 2-Explanation:
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
 2.222 2.275 2.279 None of the above

 Question 4
What does the data dictionary identify?
 Field names Field formats Field Types All of these

 Question 5
Which of the following concurrency control protocol ensures both conflict serializability and free from deadlock?
 Time stamp ordering 2 Phase locking Both (a) and (b) None of the above

Question 5-Explanation:
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
 Atomicity, consistency, isolation, database Atomicity, consistency, isolation, durability Atomicity, consistency, integrity, durability Atomicity, consistency, integrity, database

Question 6-Explanation:
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);```
 16 4 8 None of the above none

Question 7-Explanation:
(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?
 Double ellipse Dashed ellipse Squared ellipse Ellipse with attribute name underlined

Question 8-Explanation:
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
 {1, 3, 5, 6, 7, 8} {2, 4, 9} {2, 4} {1, 2, 3, 4, 5, 6, 7, 8, 9}

Question 9-Explanation:
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
 Both NP-complete Both in P NP-complete and in P, respectively Undecidable and NP-complete, respectively

Question 10-Explanation:
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.
There are 78 questions to complete.