Relations and Functions
Question
Question 1 : Which of these is not a type of relation?
1. Reflexive
2. Surjective
3. Symmetric
4. Transitive
Answer
Correct Anaswer : 2
Explanation:
Surjective is not a type of relation. It is a type of function. Reflexive, Symmetric and Transitive are type of relations.
4395
Question 2 : An Equivalence relation is always symmetric.
1. True
2. False
3. Both
4. None
Answer
Correct Anaswer : 1
Explanation:
The given statement is true. A relation R in a set A is said to be an equivalence relation if R is reflexive, symmetric and transitive. Hence, an equivalence relation is always symmetric.
4396
Question 3 : Which of the following relations is symmetric but neither reflexive nor transitive for a set A = {1, 2, 3}.
1. R = {(1, 2), (1, 3), (1, 4)}
2. R = {(1, 2), (2, 1)}
3. R = {(1, 1), (2, 2), (3, 3)}
4. R = {(1, 1), (1, 2), (2, 3)}
Answer
Correct Anaswer : 2
Explanation:
A relation in a set A is said to be symmetric if (a1, a2)∈R implies that (a1, a2)∈R,for every a1, a2∈R.
Hence, for the given set A={1, 2, 3}, R={(1, 2), (2, 1)} is symmetric. It is not reflexive since every element is not related to itself and neither transitive as it does not satisfy the condition that for a given relation R in a set A if (a1, a2)∈R and (a2, a3)∈R implies that (a1, a3)∈ R for every a1, a2, a3∈R.
4397
Question 4 : Which of the following relations is transitive but not reflexive for the set S={3, 4, 6}?
1. R = {(3, 4), (4, 6), (3, 6)}
2. R = {(1, 2), (1, 3), (1, 4)}
3. R = {(3, 3), (4, 4), (6, 6)}
4. R = {(3, 4), (4, 3)}
Answer
Correct Anaswer : 1
Explanation:
Explanation: For the above given set S = {3, 4, 6}, R = {(3, 4), (4, 6), (3, 6)} is transitive as (3,4)∈R and (4,6) ∈R and (3,6) also belongs to R . It is not a reflexive relation as it does not satisfy the condition (a,a)∈R, for every a∈A for a relation R in the set A.
4398
Question 5 : Let R be a relation in the set N given by R={(a,b): a+b=5, b>1}. Which of the following will satisfy the given relation?
1. (2,3) ∈ R
2. (4,2) ∈ R
3. (2,1) ∈ R
4. (5,0) ∈ R
Answer
Correct Anaswer : 1
Explanation:
(2,3) ∈ R as 2+3 = 5, 3>1, thus satisfying the given condition.
(4,2) doesn’t belong to R as 4+2 ≠ 5.
(2,1) doesn’t belong to R as 2+1 ≠ 5.
(5,0) doesn’tbelong to R as 0⊁1
4399