Which is the roster form of N={x:x∈N, 15<x<25, x is prime}?
Answer and explanation
Correct answer: N={17,19,23}
The strict inequalities require natural numbers greater than 15 and less than 25, so candidates run from 16 through 24. Testing primality leaves 17, 19, and 23; the other candidates are composite. The endpoint 25 is excluded because the upper inequality is strict. Therefore the exact roster form is {17,19,23}, making option A correct.
Frequently asked questions
What is the correct answer to this question?
N={17,19,23}
Why is this the correct answer?
The strict inequalities require natural numbers greater than 15 and less than 25, so candidates run from 16 through 24. Testing primality leaves 17, 19, and 23; the other candidates are composite. The endpoint 25 is excluded because the upper inequality is strict. Therefore the exact roster form is {17,19,23}, making option A correct.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems.
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