If E = {x : x is a positive factor of 18 and x is prime}, what is E?
Answer and explanation
Correct answer: E = {2, 3}
First list the positive factors of 18: 1, 2, 3, 6, 9 and 18. Then apply the second condition, namely that the factor must be prime. Only 2 and 3 have exactly two positive divisors. The number 1 is neither prime nor composite, while 6, 9 and 18 are composite. Therefore E = {2, 3}, making option A correct.
Frequently asked questions
What is the correct answer to this question?
E = {2, 3}
Why is this the correct answer?
First list the positive factors of 18: 1, 2, 3, 6, 9 and 18. Then apply the second condition, namely that the factor must be prime. Only 2 and 3 have exactly two positive divisors. The number 1 is neither prime nor composite, while 6, 9 and 18 are composite. Therefore E = {2, 3}, making option A correct.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems. Topic: General chapter practice.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
