Q5 of 23 Page 30

Write the following sets in roster form.

(i) B = {x : x is a natural number smaller than 6}


(ii) C = {x : x is a two-digit natural number such that the sum of its digits is 8}.


(iii) D = {x : x is a prime number which is a divisor of 60}.


(iv) E = {x : x is an alphabet in BETTER}.

We know that in roster method, we write all the elements of a set in curly brackets. Each of the element is written only once and separated by commas. The order of the element is not important but it is necessary to write all the elements of the set.


(i) B = {x: x is a natural number smaller than 6}


Natural numbers are 1, 2, 3 …


∴ B = (1, 2, 3, 4, 5}


(ii) C = {x: x is a two-digit natural number such that the sum of its digits is 8}.


8 can be the sum of digits when the two digits are 1, 7 (or) 2, 6 (or) 3, 5 (or) 4, 4.


∴ C = {17, 26, 35, 44, 53, 62, 71}


(iii) D = {x: x is a prime number which is a divisor of 60}.


The prime factorization of 60 = 22 × 3 × 5


∴ D = {3, 5}


(iv)E = {x: x is an alphabet in BETTER}.


∴ E = {B, E, T, R}


More from this chapter

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3

Express the following statements using symbols.

(i) The elements ‘x’ does not belong to ‘A’.


(ii) ‘d’ is an element of the set ‘B’.


(iii) ‘1’ belongs to the set of Natural numbers N.


(iv) ‘8’ does not belong to the set of prime numbers P.

 4

State whether the following statements are true or false. Justify your answer

(i) 5 set of prime numbers


(ii) S = {5, 6, 7} implies 8 ∈S.


(iii) -5 W where ‘W’ is the set of whole numbers


(iv) Z where ‘Z’ is the set of integers.

 6

Write the following sets in the set-builder form.

(i) {3, 6, 9, 12}


(ii) {2, 4, 8, 16, 32}


(iii) {5, 25, 125, 625}


(iv) {1, 4, 9, 16, 25 … 100}

 7

Write the following sets in roster form.

(i) A = {x : is a natural number greater than 50 but smaller than 100}


(ii) B = {x : x is an integer, x2 = 4}


(iii) D = {x : x is a letter in the word “LOYAL”}