Question

If U ={x | x ∈N, x < 10} and A = {x | x ∈N, 2 ≤ x < 6} then (A′)′ is
(a) {1, 6, 7, 8, 9}
(b) {1, 2, 3, 4}
(c) {2, 3, 4, 5}
(d) { }

Answer 1

(A')' = A= {2, 3, 4, 5}
so, the correct answer is (C)

Answer 2

Solution :

i ) U = { x/x€N , x <10 }

U = { 1,2,3,4,5,6,7,8 , 9 }

ii ) A = { x/x€N , 2≤x<6 }

= { 2,3,4,5 }

iii ) A' = U - A

= {1,2,3,4,5,6,7,8,9}- {2,3,4,5}

= { 1,6,7,8,9 }

iv) ( A' )' = U - A'

= {1,2,3,4,5,6,7,8,9 } - {1,6,7,8,9}

= { 2,3,4,5 }

= A

Therefore ,

( A' )' = A

Option ( C ) is. Correct.

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