Which of the following are sets ? Justify your answer.

The collection of all boys in your class.

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The collection of all boys in your class is a well-defined collection because you can definitely identify a boy who belongs to this collection.

Hence, this collection is a set.

Similar Questions

Let $A=\{1,2,3,4,5,6\} .$ Insert the appropriate symbol $\in$ or $\notin$ in the blank spaces:

$ 2 \, ....... \, A $

For an integer $n$ let $S_n=\{n+1, n+2, \ldots \ldots, n+18\}$. Which of the following is true for all $n \geq 10$ ?

  • [KVPY 2013]

List all the elements of the following sers :

$A = \{ x:x$ is an odd natural number $\} $

Match each of the set on the left described in the roster form with the same set on the right described in the set-builder form:

$(i)$  $\{ P,R,I,N,C,A,L\} $ $(a)$  $\{ x:x$ is a positive integer and is adivisor of $18\} $
$(ii)$  $\{ \,0\,\} $ $(b)$  $\{ x:x$ is an integer and ${x^2} - 9 = 0\} $
$(iii)$  $\{ 1,2,3,6,9,18\} $ $(c)$  $\{ x:x$ is an integer and $x + 1 = 1\} $
$(iv)$  $\{ 3, - 3\} $ $(d)$  $\{ x:x$ is aletter of the word $PRINCIPAL\} $

 

The number of non-empty subsets of the set $\{1, 2, 3, 4\}$ is