Which option is a suitable set-builder form of Z = {5, 10, 15, 20}?
Answer and explanation
Correct answer: Z = {x : x is a multiple of 5 and 5 ≤ x ≤ 20}
A correct set-builder description must generate every listed element and no extra element. Each member of Z is a multiple of 5, and the inclusive bounds 5 ≤ x ≤ 20 restrict the multiples to 5, 10, 15, and 20 exactly. Option B also includes 1, 2, 4, and 20; option C includes many even numbers; option D gives primes. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
Z = {x : x is a multiple of 5 and 5 ≤ x ≤ 20}
Why is this the correct answer?
A correct set-builder description must generate every listed element and no extra element. Each member of Z is a multiple of 5, and the inclusive bounds 5 ≤ x ≤ 20 restrict the multiples to 5, 10, 15, and 20 exactly. Option B also includes 1, 2, 4, and 20; option C includes many even numbers; option D gives primes. Therefore option A is correct.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Common Questions. Topic: General chapter practice.
