If U = {x ∈ N : x ≤ 15} and A = {x : x is a multiple of 5}, what is n(A′)?
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Answer and explanation
Correct answer: 12
Assuming N denotes the positive natural numbers, U = {1,2,3,...,15}, so n(U) = 15. The multiples of 5 that lie in U are A = {5,10,15}, giving n(A) = 3. Since A′ contains the elements of U outside A, n(A′) = n(U) − n(A) = 15 − 3 = 12. Thus option D is correct.
Frequently asked questions
What is the correct answer to this question?
12
Why is this the correct answer?
Assuming N denotes the positive natural numbers, U = {1,2,3,...,15}, so n(U) = 15. The multiples of 5 that lie in U are A = {5,10,15}, giving n(A) = 3. Since A′ contains the elements of U outside A, n(A′) = n(U) − n(A) = 15 − 3 = 12. Thus option D is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Complement of a Set and Its Properties.
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