Page 14 - Mathematics Class - XI

Viva-Voce

1. What is meant by A ∪ B?
Ans. The union of A and B is the set of all those elements which belong either A or to B or to both A and B.

2. What is meant by A ∩ B?
Ans. The intersection of A and B is the set of all those elements that belong to both A and B.
3. What is meant by disjoint sets?

Ans. Two sets are said to be disjoint sets if they have no element in common.
OR

Two disjoint sets are sets whose intersection is the empty set.
4. If A and B are two sets, then find:
(a) (A – B) ∩ (B – A) (b) (A – B) ∪ (A ∩ B)

Ans. (a) φ (b) A
5. If A and B are two sets such that A ⊂ B, then find:

(a) A ∩ B (b) A ∪ B
Ans. (a) A (b) B
6. What are Venn diagrams?

Ans. Venn diagrams are the diagrams which represent the relationship between sets.

MCQs

1. The complement of (A') is written by

a) A'A b) (A')' c) A d) None of these
2. Set (A ∩ B')' ∪ (B ∩ C) is equal to the set

a) A' ∪ B ∪ C b) A' ∪ B c) A' ∪ C' d) A' ∪ B
3. In a city of 840 persons, 450 persons read Hindi, 300 persons read English and 200 persons read both
subjects, then the number of persons does not read any subject.
a) 210 b) 290 c) 180 d) 260

4. n(A) – n(A ∩ B) is equal to
a) n(A + B) b) nA – B c) n(A – B) d) None of these

5. A – B equal to
a) A ∩ B b) A ∪ B c) A ∩ B' d) None of these

Answers: 1. b) (A')' 2. b) A' ∪ B 3. b) 290 4. c) n(A – B) 5. c) A ∩ B'

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