Question

A={X|X is a prime number 10 < x <25) B = { 13, 15,17,19,21} find AUB , A∩B , A-B
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Answer 1

Answer:

Exercise 1.1

Question 1:

Which of the following are sets? Justify your answer.

(i) The collection of all months of a year beginning with the letter J.

(ii) The collection of ten most talented writers of India.

(iii) A team of eleven best-cricket batsmen of the world.

(iv) The collection of all boys in your class.

(v) The collection of all natural numbers less than 100.

(vi) A collection of novels written by the writer Munshi Prem Chand.

(vii) The collection of all even integers.

(viii) The collection of questions in this Chapter.

(ix) A collection of most dangerous animals of the world.

Answer:

(i) The collection of all months of a year beginning with the letter J is a well-defined collection

of objects because one can definitely identify a month that belongs to this collection.

Hence, this collection is a set.

(ii) The collection of ten most talented writers of India is not a well-defined collection because

the criteria for determining a writer’s talent may vary from person to person.

Hence, this collection is not a set.

(iii) A team of eleven best cricket batsmen of the world is not a well-defined collection because

the criteria for determining a batsman’s talent may vary from person to person.

Hence, this collection is not a set.

(iv) The collection of all boys in your class is a well-defined collection because we can

definitely identify a boy who belongs to this collection.

Hence, this collection is a set.

(v) The collection of all natural numbers less than 100 is a well-defined collection because one

can definitely identify a number that belongs to this collection.

Hence, this collection is a set.

(vi) A collection of novels written by the writer Munshi Prem Chand is a well-defined collection

because one can definitely identify a book that belongs to this collection.

Hence, this collection is a set.

(vii) The collection of all even integers is a well-defined collection because one can definitely

identify an even integer that belongs to this collection.

Hence, this collection is a set.

(viii) The collection of questions in this chapter is a well-defined collection because one can

definitely identify a question that belongs to this chapter.

Hence, this collection is a set.

(ix) The collection of most dangerous animals of the world is not a well-defined collection

because the criteria for determining the dangerousness of an animal can vary from person to

person.

Hence, this collection is not a set.

Question 2:

Let A = {1, 2, 3, 4, 5, 6}. Insert the appropriate symbol ∈ or ∉ in the blank spaces:

(i) 5...A (ii) 8...A (iii) 0...A (iv) 4...A (v) 2...A (vi) 10...A

Answer:

Given set A = {1, 2, 3, 4, 5, 6}

(i) Since the number 5 is in the set A. So, 5 ∈ A

(ii) Since the number 8 is not in the set A. So, 8 ∉ A

(iii) Since the number 0 is not in the set A. So, 0 ∉ A

(iv) Since the number 4 is in the set A. So, 4 ∈ A

(v) Since the number 2 is in the set A. So, 2 ∈ A

(vi) Since the number 10 is not in the set A. So, 10 ∉ A

Question 3:

Write the following sets in roster form:

(i) A = {x: x is an integer and –3 < x < 7}.

(ii) B = {x: x is a natural number less than 6}.

(iii) C = {x: x is a two-digit natural number such that the sum of its digits is 8}

(iv) D = {x: x is a prime number which is divisor of 60}.

Step-by-step explanation:

Its your answer.....