Question

Which of the following set is finite?

(a) {1,2,3,4,……………………….}

(b) {4,7,9}

(c) {1,4,9,16,…………………….}

(d) {1,8,27,……………………….}

This question was posed to me in class test.

The doubt is from Finite and Infinite Sets topic in chapter Sets of Mathematics – Class 11

Answer 1

Correct option is (b) {4,7,9}

To elaborate: {4,7,9} is finite set because it contains finite (countable) number of elements. Rest all are infinite sets. {1,2,3,4,…………..} is a set of natural numbers. {1,4,9,……………} is a set of square of natural numbers. {1,8,27,………………………} is a set of cube of natural numbers.