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9th Maths English Medium (Unit 1 Set Theory)Assignment Answerkey 2021

9th Maths English Medium (Unit 1 Set Theory)Assignment Answerkey 2021: As per the government educational department’s decision all schools collecting assignments from students. but some students need full answer key to verify their assignments to help those students we created this assignment answer key please download is print for your future references

9th Maths English Medium (Unit 1 Set Theory)Assignment Answerkey 2021

9th maths 1st unit assignment – Question Only download here

Assignment
Class:9 Subject:Mathematics
Unit 1- Set Theory


Part- A



I. 1 Mark Questions :

1.Consider the set A={10, 15, 20, 25}. Fill in the blanks with the appropriate symbol ∈ or € 
i) 10………. A ii) 23…….. A

Answer:-  i) 10 ∈ A          ii) 23 € A


2.Write set of letters of the following word in Roster Form
MATHEMATICS

Answer:-  A={M,A,T,H,E,I,C,S}


3.If A={8, 10, 12, 14, 16, 18, 20} find n(A)
a. 4 b. 8 c. 7 d. 6

Answer:-   c. 7


4.If A={4, 5, 6}and B={3, 5, 7} (A∩B) 
a. { 5 } b. { 4 } c. { 5, 6 } d. { 5, 7 }

Answer:-   a. { 5 }


5.Which of the following is correct?
a. ∅⊂ { a, b }  b.  ∅∈ { a, b }    c. {a} ∈ { a, b }    d. a ∈ { a, b }  

Answer:-   a. ∅⊂ { a, b } 


6.Which of the following is correct?
a. { 8 } ∈ { 1, 2, 3, 7 }           b. { 8 } € { 1, 2, 3, 7 }  
c. 7 ∈{ 1, 2, 3, 7 } d.  { 7 } € { 1, 2, 3}    

Answer:-   a. { 8 } ∈ { 1, 2, 3, 7 }  


7.Which of the following is true?
a. A-B=(AB) b. A-B=B-A
c. (AB)’ = A’B’ d. (AB)’ = AB’

Answer:-    d. (A∩B)´ = A´∪B´


8.If A and B are disjoint sets then n(A B) = n(A) + n(B). This statement is
a. True b. False

Answer:-     b. False


9.Fill in the blank
A- (B C) = _____

Answer:-     (A-B)∪(A-C)


10.For any two sets A and B
i). A B = B A ii). A B= B A this property is


a). Associate Property b). Distributive Property
c). Commutative Property d). None of these.

Answer:-     a). Associate Property



Part- B


II. Short Answer:

1.If A={2,5,7,8,9} and B= {7,8,10,11} find A Δ B

Answer

A -B = {2,5,9 }

B-A = {10,11}

AΔB = (A-B) (B_A)

= { 2,5,9 } {10,11}

= {2,5,9,10,11}


2.Find the Number of subsets & the number of proper subsets of a set A ={x,y,z,p,q}.

Anwer
Given A = {x,y,z,p,q}

n(A) = 5

No.of Subsets =2m = 25 = 2x2x2x2x2x = 32

No.of Proper Subsets = 2m-1 = 25 -1 = 32-1 = 31


3.Write the set of letters of the following words in Roster form,
i). ASSIGNMENT ii). TEACHER

Answer

i) {A,S,I,G,N,M,E,T}

ii){T,E,A,C,H,R}


4.A={1,2,5,7,9}, Q={2,3,5,9,11}, R={3,4,5,7,9} and S={2,3,4,5,8}, then find
i). (P Q) R ii). (Q S) R

Answers

i) (P Q) = {1,2,5,7,9} {2,3,5,9,11}

= {1,2,3,5,7,9,11}

(P Q) R = {1,2,3,5,7,9,11} {3,4,5,7,9}

= {1,2,3,4,5,7,9,11}

ii) (Q S) ={2,3,5,9,11} {2,3,4,5,8}

= {2,3,5}

(Q S) R = {2,3,5} {3,4,5,7,9}

= {3,5}


5.If n(A) = 20, n(B) = 50, n(A U B) = 60 and n(B’ ) = 20, find n(A B) and n(U)

n(A U B) = n(A) + n (A B)

60 = 20 + 50 – n (A B)

60 = 70 – n (A B)

b(A B) = 70-60

n(A B) = 10

n( U ) = n(B) + n (B’)

= 50+20

=70



Part- C


III. Answer the following:

1.Let X={a, e, i, o, u}and Y={a, g, o, f}. Verify that n(A-B) = n(A) – n(AB)

2.Out of 500 Car owners investigated, 400 owned Car A and 200 Owned Car B, 50 Owned
both A and B Cars. Is this data Correct?

Solution:
n( A ∪ B) = n(A) + n(B) – n( A ∩ B)
n(A ∪ B) = 500 (given) …………. (1).
n( A) = 400
n(B) = 200
n( A ∩ B) =50
∴ n(A ∩ B) = 400 + 200 – 50 = 550 …………… (2)
1 ≠ 2
∴ This data is incorrect.