Question

Write the following sets in roster form.(i) B = {x : x is a natural number less 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 = {the set of all letters in the word BETTER}.

Answer 1

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

So, x in roaster form {1,2,3,4,5}

6 is excluded because x<6

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

let x =m+n

if m =1,2,3,4,5,6,7

then n=7,6,5,4,3,2,1

So, m+n=8

Hence, x in roaster form{17,26,35,44,53,62,71}

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

60 =2*2*3*5

So, x in roaster form {2,3,5}

iv) E = {the set of all letters in the word BETTER}

So,E in roaster form{B,E,T,R}