Let A = {x ∈ ℕ : 1 ≤ x ≤ 50 and x is divisible by 7}, where ℕ = {1, 2, 3, …}. What is n(A)?
Answer and explanation
Correct answer: 7
The positive multiples of 7 that do not exceed 50 are 7, 14, 21, 28, 35, 42, and 49. The next multiple, 56, is greater than 50, so it is excluded. Thus A has seven elements, and its cardinality is n(A) = 7. The explicit positive-number convention also prevents 0 from being counted.
Frequently asked questions
What is the correct answer to this question?
7
Why is this the correct answer?
The positive multiples of 7 that do not exceed 50 are 7, 14, 21, 28, 35, 42, and 49. The next multiple, 56, is greater than 50, so it is excluded. Thus A has seven elements, and its cardinality is n(A) = 7. The explicit positive-number convention also prevents 0 from being counted.
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.