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Easy · Level 8 · less than equal,reflexive relation,exam mcqView options
Yes, because (a\le a) for every (a)
No, because (1\le 2)
No, because (3\le 1) is false
Yes, only because (A) has three elements
Question 1EasyLevel 7
If (A={1,2,3}), which pair will always be present in every reflexive relation on (A)?
Correct answer: A
Step 1: Every reflexive relation contains all self-pairs. Step 2: Since (2 \in A), ((2,2)) must be present in every reflexive relation. Step 3: Pairs with different elements are not always required.
On (A={1,2,3}), (R) is reflexive. Which statement is not necessary?
Correct answer: A
Step 1: Reflexivity makes only self-pairs compulsory. Step 2: ((1,2)) is not a self-pair, so it is not necessary. Step 3: Pay attention to the phrase not necessary in the question.
How many pairs are there in the identity relation on (A={1,2,3,4})?
Correct answer: A
Step 1: The identity relation contains only self-pairs. Step 2: (A) has 4 elements, so it has 4 pairs. Step 3: The identity relation and minimum reflexive relation have the same count.
If (A={1,2,3}) and (R={(1,1),(2,2),(3,3)}), what is the correct statement about (R)?
Correct answer: A
Step 1: The given (R) has all self-pairs. Step 2: It has no extra pair, so it is the minimum reflexive relation. Step 3: The minimum reflexive relation is also the identity relation.
On (A={1,2,3}), (R={(1,1),(2,2),(3,3),(1,2),(2,3),(3,1)}). Is (R) reflexive?
Correct answer: A
Step 1: Identify the required self-pairs separately. Step 2: ((1,1),(2,2),(3,3)) are present, so (R) is reflexive. Step 3: Do not change the answer because of extra cyclic pairs.
On (A={1,2,3}), (R={(1,1),(2,2),(2,3),(3,1)}). Why does reflexivity fail?
Correct answer: A
Step 1: All self-pairs of (A) are required. Step 2: For (3), ((3,3)) is necessary but not given. Step 3: Even if other pairs are present, one missing self-pair fails reflexivity.
What should be checked first while testing a reflexive relation?
Correct answer: A
Step 1: Reflexive relation is identified by self-pairs. Step 2: So the first task is to check ((a,a)) for every element. Step 3: Check symmetric or other properties later.
On (A={1,2,3,4}), (R) is reflexive. Which pair must be in (R)?
Correct answer: A
Step 1: In a reflexive relation, each element of (A) is related to itself. Step 2: Since (4 \in A), ((4,4)) must be present. Step 3: Do not treat pairs with different elements as compulsory.
If (R) is not reflexive, which situation may occur?
Correct answer: A
Step 1: Not reflexive means at least one required self-pair is missing. Step 2: So for some (a \in A), ((a,a) \notin R). Step 3: Understanding the opposite condition helps identify the property quickly.
On (A={1,2,3}), (R={(a,b):a=b\text{ or }a+b\text{ is even}}). Is (R) reflexive?
Correct answer: A
Step 1: To test reflexivity, put ((a,a)) in the rule. Step 2: For ((a,a)), (a=b) is true, so every self-pair is included. Step 3: In an or condition, one true condition is enough.
If (A={1,2,3}), which ordered pairs must be present in a relation on (A) for it to be reflexive?
Correct answer: B
Step 1: In a reflexive relation every element must be related to itself. Step 2: So for (1,2,3), the required pairs are ((1,1),(2,2),(3,3)). Step 3: In exams, check diagonal pairs first.
On the set (A={a,b}), (R={(a,a),(a,b),(b,b)}) is given. What is (R)?
Correct answer: A
Step 1: For elements (a) and (b), the pairs ((a,a)) and ((b,b)) are required. Step 2: Both pairs are present in (R), so the extra pair does not matter. Step 3: Reflexivity only needs all self-pairs.
If (A={2,4,6}) and (R={(2,2),(4,4)}), why is (R) not reflexive?
Correct answer: C
Step 1: A reflexive relation must contain the self-pair of every element of (A). Step 2: For (6), the pair ((6,6)) is missing. Step 3: If even one required pair is absent, the relation is not reflexive.
To make a relation (R) reflexive on (A={5,7}), what is the minimum set of pairs required?
Correct answer: B
Step 1: The smallest reflexive relation contains only the required self-pairs. Step 2: For (5) and (7), the needed pairs are ((5,5)) and ((7,7)). Step 3: Extra pairs are not compulsory.
If (R=A\times A) on (A={1,2}), which statement about (R) is correct?
Correct answer: A
Step 1: (A\times A) contains all possible ordered pairs from (A). Step 2: It includes ((1,1)) and ((2,2)), so it is reflexive. Step 3: The universal relation is always reflexive.
Choose the correct statement about the empty relation on a non-empty set (A).
Correct answer: B
Step 1: A non-empty set has at least one element. Step 2: The empty relation has no self-pairs. Step 3: Therefore, it is not reflexive on a non-empty set.
On (A={1,2,3,4}), how many pairs must a reflexive relation have at minimum?
Correct answer: C
Step 1: A reflexive relation needs one self-pair for each element. Step 2: (A) has (4) elements, so at least (4) pairs are needed. Step 3: The minimum count equals the number of elements.
If (A={x,y,z}), which of the following relations is reflexive?
Correct answer: B
Step 1: For (x,y,z), all three self-pairs ((x,x),(y,y),(z,z)) are required. Step 2: Only the second relation contains all three. Step 3: Extra pairs do not break reflexivity.
On (A={1,2,3}), (R={(a,b):a\le b}) is given. Is (R) reflexive?
Correct answer: A
Step 1: Reflexivity needs ((a,a)) for every (a\in A). Step 2: Every number is less than or equal to itself, so (a\le a) is true. Step 3: The relation (\le) is generally reflexive.
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