If U = {1,2,...,20} and A′ = {2,3,5,7,11,13,17,19}, what is the set A?
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Answer and explanation
Correct answer: {1,4,6,8,9,10,12,14,15,16,18,20}
A and A′ are complementary subsets of U, so A = U \ A′. Remove 2, 3, 5, 7, 11, 13, 17, and 19 from the numbers 1 through 20. The remaining elements are 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, and 20. Notice that 1 remains because it is neither prime nor listed in A′.
Frequently asked questions
What is the correct answer to this question?
{1,4,6,8,9,10,12,14,15,16,18,20}
Why is this the correct answer?
A and A′ are complementary subsets of U, so A = U \ A′. Remove 2, 3, 5, 7, 11, 13, 17, and 19 from the numbers 1 through 20. The remaining elements are 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, and 20. Notice that 1 remains because it is neither prime nor listed in A′.
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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