If A = {x ∈ N : x is an n-digit number, where n = 1}, what is the number of elements in A?
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Answer and explanation
Correct answer: 9
When n = 1, A consists of all one-digit natural numbers. Under the standard school convention N = {1, 2, 3, ...}, these numbers are 1, 2, 3, 4, 5, 6, 7, 8, and 9. The number 0 is not a one-digit natural number in this convention. Therefore, A has 9 elements, making option A correct.
Frequently asked questions
What is the correct answer to this question?
9
Why is this the correct answer?
When n = 1, A consists of all one-digit natural numbers. Under the standard school convention N = {1, 2, 3, ...}, these numbers are 1, 2, 3, 4, 5, 6, 7, 8, and 9. The number 0 is not a one-digit natural number in this convention. Therefore, A has 9 elements, making option A correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: The Empty Set, Finite and Infinite Sets, Equal Sets.
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