NCERT Class XI Mathematics - Sets - Solutions

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Question : 3
Total: 73
Write the following sets in roster form:
(i) A = {x : x is an integer and –3 < x < 7}
(ii) B = {x : x is a natural number less than 6}
(iii) C = {x : x is a two-digit natural number such that the sum of its digits is 8}
(iv) D = {x : x is a prime number which is divisor of 60}
(v) E = The set of all letters in the word TRIGONOMETRY
(vi) F = The set of all letters in the word BETTER
Solution:  
(i) Integers lying between –3 and 7 are –2, –1, 0, 1, 2, ....., 6
∴ A = {–2, –1, .... , 6}.
(ii) Natural numbers less than 6 are 1, 2, 3, 4, 5.
∴ B = {1, 2, 3, 4, 5}
(iii) Two digit natural numbers such that the sum of its digits is 8 are 17,
26, 35, 44, 53, 62, 71, 80.
∴ C = {17, 26, 35, 44, 53, 62, 71, 80}
(iv) Prime number divisors of 60 are 2, 3, 5. \ D = {2, 3, 5}
(v) Word TRIGONOMETRY is formed by using the letters T, R, I, G, O, N, M, E, Y.
∴ E = {T, R, I, G, N, O, M, E, Y}
(vi) Word BETTER is formed by using the letters B, E, T, R
∴ F = {B, E, T, R}
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