If A = {x ∈ N : x is divisible by 5 and x ≤ 100}, what is n(A)?
Answer and explanation
Correct answer: 20
The natural-number elements of A are the positive multiples of 5 not exceeding 100: 5, 10, 15, ..., 100. Each multiple has the form 5k, where k = 1, 2, ..., 20. Equivalently, the number of terms is 100 ÷ 5 = 20. Because 100 itself is divisible by 5 and satisfies x ≤ 100, it is included.
Frequently asked questions
What is the correct answer to this question?
20
Why is this the correct answer?
The natural-number elements of A are the positive multiples of 5 not exceeding 100: 5, 10, 15, ..., 100. Each multiple has the form 5k, where k = 1, 2, ..., 20. Equivalently, the number of terms is 100 ÷ 5 = 20. Because 100 itself is divisible by 5 and satisfies x ≤ 100, it is included.
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.