Describe the following sets in Roster form:

{x:x is a letter before e in the English alphabet}.

Which of the following collections are sets? Justify your answer:

(i) A collection of all natural numbers less than 50.

(ii) The collection of good hockey players in India.

(iii) The collection of all the girls in your class.

(iv) The collection of all talented writers of India.

(v) The collection of difficult topics in Mathematics.

(vi) The collection of novels written by Munshi Prem Chand.

(vii) The collection of all questions of this chapter.

(viii) The collection of all months of a year beginning with the letter J.

(ix) A collection of most dangerous animals of the world.

(x) The collection of prime integers.

If A={0,1,2,3,4,5,6,7,8,9,10}, then insert the appropriate symbol or in each of the following blank spaces:

i. 4 ……A ii. -4……A

iii. 12…..A iv. 9…..A

v. 0……A vi. -2……A

Describe the following sets in Roster form:

{x N: x²< 25}.

Describe the following sets in Roster form:

{x N: x is a prime number, 10 < x < 20}