# If A = {3, 6, 9, 12, 15, 18, 21}, B = { 4, 8, 12, 16, 20 }, C = { 2, 4, 6, 8, 10, 12, 14, 16 }, D = {5, 10, 15, 20 }; find

(i) A – B (ii) A – C (iii) A – D (iv) B – A (v) C – A (vi) D – A (vii) B – C (viii) B – D (ix) C – B (x) D – B (xi) C – D (xii) D – C

**Solutions:**

The given sets are:

- A = {3, 6, 9, 12, 15, 18, 21}
- B = { 4, 8, 12, 16, 20 }
- C = { 2, 4, 6, 8, 10, 12, 14, 16 }
- D = {5, 10, 15, 20 }

The difference between two sets A and B is a set denoted by A - B and is obtained by writing the elements of A that are NOT in B in a set.

Thus,

(i) A - B = {3, 6, 9, 15, 18, 21}

(ii) A - C = {3, 9, 15, 18, 21}

(iii) A - D = {3, 6, 9, 12, 18, 21}

(iv) B - A = {4, 8, 16, 20}

(v) C - A = {2, 4, 8, 10, 14, 16}

(vi) D - A = {5, 10, 20}

(vii) B - C = {20}

(viii) B - D = {4, 8, 12, 16}

(ix) C - B = {2, 6, 10, 14}

(x) D - B = {5, 10, 15}

(xi) C - D = {2, 4, 6, 8, 12, 14, 16}

(xii) D - C = {5, 15, 20}

NCERT Solutions Class 11 Maths Chapter 1 Exercise 1.4 Question 9

## If A = {3, 6, 9, 12, 15, 18, 21}, B = { 4, 8, 12, 16, 20 }, C = { 2, 4, 6, 8, 10, 12, 14, 16 }, D = {5, 10, 15, 20 }; find (i) A – B (ii) A – C (iii) A – D (iv) B – A (v) C – A (vi) D – A (vii) B – C (viii) B – D (ix) C – B (x) D – B (xi) C – D (xii) D – C

**Summary:**

It is given that A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}. We have found that

**(i) **A - B = {3, 6, 9, 15, 18, 21}

**(ii)** A - C = {3, 9, 15, 18, 21}

**(iii)** A - D = {3, 6, 9, 12, 18, 21}

**(iv)** B - A = {4, 8, 16, 20}

**(v)** C - A = {2, 4, 8, 10, 14, 16}

**(vi)** D - A = {5, 10, 20}

**(vii)** B - C = {20}

**(viii)** B - D = {4, 8, 12, 16}

**(ix)** C - B = {2, 6, 10, 14}

**(x)** D - B = {5, 10, 15}

**(xi)** C - D = {2, 4, 6, 8, 12, 14, 16}

**(xii)** D - C = {5, 15, 20}

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