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# Class 11 NCERT Solutions – Chapter 1 Sets – Exercise 1.6

• Difficulty Level : Basic
• Last Updated : 27 Nov, 2020

### Question 1. If X and Y are two sets such that n(X) = 17, n(Y) = 23 and n(X âˆª Y) = 38, find n(X âˆ© Y).

Solution:

n (X) = 17

n (Y) = 23

n (X U Y) = 38

So we will write this as :

n (X U Y) = n (X) + n (Y) â€“ n (X âˆ© Y)

Putting values,

38 = 17 + 23 â€“ n (X âˆ© Y)

So,

n (X âˆ© Y) = 40 â€“ 38 = 2

âˆ´ n (X âˆ© Y) = 2

### Question 2. If X and Y are two sets such that X âˆª Y has 18 elements, X has 8 elements and Y has 15 elements; how many elements does X âˆ© Y have?

Solution:

n (X U Y) = 18

n (X) = 8

n (Y) = 15

So we will write this as :

n (X U Y) = n (X) + n (Y) â€“ n (X âˆ© Y)

Putting values,

18 = 8 + 15 â€“ n (X âˆ© Y)

So,

n (X âˆ© Y) = 23 â€“ 18 = 5

âˆ´ n (X âˆ© Y) = 5

### Question 3. In a group of 400 people, 250 can speak Hindi and 200 can speak English. How many people can speak both Hindi and English?

Solution:

Let ‘A’ is the set of people who speak Hindi & ‘B’ is the set of people who speak English

Given,

n(A âˆª B) = 400

n(A) = 250

n(B) = 200

So we will write this as :

n(A âˆª B) = n(A) + n(B) â€“ n(A âˆ© B)

Putting values,

400 = 250 + 200 â€“ n(A âˆ© B)

400 = 450 â€“ n(A âˆ© B)

So,

n(A âˆ© B) = 450 â€“ 400

âˆ´ 50 people can speak both Hindi & English.

### Question 4. If S and T are two sets such that S has 21 elements, T has 32 elements, and S âˆ© T has 11 elements, how many elements does S âˆª T have?

Solution:

Given, n(S) = 21

n(T) = 32

So we will write this as :

n (S âˆª T) = n (S) + n (T) â€“ n (S âˆ© T)

Putting values,

n (S âˆª T) = 21 + 32 â€“ 11

So,

n (S âˆª T) = 42

âˆ´ the set (S âˆª T) has 42 elements.

### Question 5. If X and Y are two sets such that X has 40 elements, X âˆªY has 60 elements and X âˆ©Y has 10 elements, how many elements does Y have?

Solution:

Given, n(X) = 40

n(X âˆª Y) = 60

So we will write this as :

n(X âˆª Y) = n(X) + n(Y) â€“ n(X âˆ© Y)

Putting values,

60 = 40 + n(Y) â€“ 10

n(Y) = 60 â€“ (40 â€“ 10) = 30

âˆ´ the set Y has 30 elements.

### Question 6. In a group of 70 people, 37 like coffee, 52 like tea, and each person likes at least one of the two drinks. How many people like both coffee and tea?

Solution:

Let ‘A’ is the set of people who like coffee & ‘B’ is the set of people who like tea

Given,

n(C âˆª T) = 70

n(A) = 37

n(B) = 52

So we will write this as :

n(A âˆª B) = n(A) + n(B) â€“ n(A âˆ© B)

Putting values,

70 = 37 + 52 â€“ n(A âˆ© B)

70 = 89 â€“ n(A âˆ© B)

So,

n(A âˆ© B) = 89 â€“ 70 = 19

âˆ´ 19 people like both coffee and tea.

### Question 7. In a group of 65 people, 40 like cricket, 10 like both cricket and tennis. How many like tennis only and not cricket? How many like tennis?

Solution:

Let ‘A’ is the set of people who like cricket & ‘B’ is the set of people who like tennis

Given,

n(A âˆª B) = 65

n(A) = 40

So we will write this as :

n(A âˆª B) = n(A) + n(B) â€“ n(A âˆ© B)

Putting values,

65 = 40 + n(B) â€“ 10

65 = 30 + n(B)

So,

n(B) = 65 â€“ 30 = 35

âˆ´ 35 people like tennis.

And we can say,

(B â€“ A) âˆª (B âˆ© A) = B

So,

n (B) = n (B â€“ A) + n (B âˆ© A)

Putting values,

35 = n (B â€“ A) + 10

n (B â€“ A) = 35 â€“ 10 = 25

âˆ´ 25 people like only tennis.

### Question 8. In a committee, 50 people speak French, 20 speak Spanish and 10 speak both Spanish and French. How many speak at least one of these two languages?

Solution:

Let ‘A’ is the set of people in the committee who speak French & ‘B’ is the set of people in the committee who speak Spanish

Given,

n(A) = 50

n(B) = 20

So we will write this as :

n(B âˆª A) = n(B) + n(A) â€“ n(B âˆ© A)

Putting values,

n(B âˆª A) = 20 + 50 â€“ 10

n(B âˆª A) = 70 â€“ 10

n(B âˆª A) = 60

âˆ´ 60 people in the committee speak at least one of these two languages i.e French & Spanish.

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