Question

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

Answer 1

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} and 

D = {5, 10, 15, 20} 

i) A – B = {3, 6, 9, 12, 15, 18, 21} – {4, 8, 12, 16, 20} = {3, 6, 9, 15, 18, 21} 

ii) A – C = {3, 6, 9, 12, 15, 18, 21} – {2, 4, 6, 8, 10, 12, 14, 16} = {3,9,15,18,21} 

iii) A – D = {3, 6, 9, 12, 15, 18, 21} – {5, 10, 15, 20} = {3,6,9,12,18,21} 

iv) B – A = {4, 8, 12, 16, 20} – {3, 6, 9, 12, 15, 18, 21} = {4, 8, 16, 20} 

v) C – A = {2, 4, 6, 8, 10, 12, 14, 16} – {3, 6, 9, 12, 15, 18, 21} = {2, 4, 8, 10, 14, 16} 

vi) D – A = {5, 10, 15, 20} – {3, 6, 9, 12, 15, 18, 21} = {5, 10, 20} 

vii) B – C = {4, 8, 12, 16, 20} – {2, 4, 6, 8, 10, 12, 14, 16} = {20} 

viii) B – D = {4, 8, 12, 16,20} – {5, 10, 15, 20} = {4,8, 12, 16} 

ix) C – B = {2, 4, 6, 8, 10, 12, 14, 16} – {4, 8, 12, 16, 20} = {2, 6, 10, 14} 

x) D – B = {5, 10, 15, 20} – {4, 8, 12, 16, 20} = {5, 10, 15}