Question

Which of the following collections are sets?

All the natural numbers less than $20$ which are perfect square

Answer 1

As we know that a set is a collection of well-defined object$.$

The given statement $\text{'}$All the natural numbers less than $20$ which is perfect square$\text{'}$ is a well-defined statement$.$

The natural number starts with one and goes up to infinity.

Required natural numbers less than $20$ and which are perfect square are $1,4,9,16$

Hence$,$ the statement $\text{'}$ All the natural numbers less than $20$ which are perfect square $\text{'}$ is a collection of a set$.$