What is the roster form of S = {x ∈ N : x is prime and 10 < x < 25}?
Answer and explanation
Correct answer: S = {11, 13, 17, 19, 23}
We inspect the natural numbers strictly between 10 and 25 and retain only primes. The prime numbers in that interval are 11, 13, 17, 19, and 23. Numbers such as 15 and 21 are composite, so they cannot be included. The endpoints 10 and 25 are excluded by the strict inequalities; 25 is also composite. Hence option A is the correct roster form.
Frequently asked questions
What is the correct answer to this question?
S = {11, 13, 17, 19, 23}
Why is this the correct answer?
We inspect the natural numbers strictly between 10 and 25 and retain only primes. The prime numbers in that interval are 11, 13, 17, 19, and 23. Numbers such as 15 and 21 are composite, so they cannot be included. The endpoints 10 and 25 are excluded by the strict inequalities; 25 is also composite. Hence option A is the correct roster form.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
