If L = {x : x ∈ ℕ, x ≤ 20, x is not divisible by 2 but is divisible by 3}, what is the roster form of L?
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Answer and explanation
Correct answer: L = {3, 9, 15}
First list the multiples of 3 not exceeding 20: 3, 6, 9, 12, 15, and 18. The phrase “not divisible by 2” removes the even numbers 6, 12, and 18. The remaining odd multiples of 3 are 3, 9, and 15. The number 21 is excluded because it is greater than 20. Hence L = {3, 9, 15}.
Frequently asked questions
What is the correct answer to this question?
L = {3, 9, 15}
Why is this the correct answer?
First list the multiples of 3 not exceeding 20: 3, 6, 9, 12, 15, and 18. The phrase “not divisible by 2” removes the even numbers 6, 12, and 18. The remaining odd multiples of 3 are 3, 9, and 15. The number 21 is excluded because it is greater than 20. Hence L = {3, 9, 15}.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
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