If B = {x : x ∈ N and x is a multiple of 5 less than 20}, what is n(B)?
Answer and explanation
Correct answer: 3
The natural multiples of 5 below 20 are 5, 10, and 15. The next multiple, 20, is excluded because the condition says less than 20, not less than or equal to 20. Thus B has three distinct elements and n(B) = 3. There is no need to include 0 under the usual natural-number convention used here.
Frequently asked questions
What is the correct answer to this question?
3
Why is this the correct answer?
The natural multiples of 5 below 20 are 5, 10, and 15. The next multiple, 20, is excluded because the condition says less than 20, not less than or equal to 20. Thus B has three distinct elements and n(B) = 3. There is no need to include 0 under the usual natural-number convention used here.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Common Questions.
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