Question

Write A={x:x is a natural number and x square <40} in roster form​

Answer 1

A = {1, 2, 3, 4, 5, 6}

Explanation:

★ Here, x is a natural number because natural numbers start from 1 to infinity.

★ The square of all numbers is less than 40. Consider only upto 6 because 7² would be 49 which is greater than 40

KNOW MORE:

• All sets can be represented in either set builder form or roster form.
• Roster form is mainly used for countable set of numbers like the one used here.
• Set builder form is mainly used for uncountable set of numbers.

Ex: B = {x: x ∈ N where x is divisible by 3}

There are infinitely many numbers which are divisible by 3 and it is not possible to write all of them in 1 set. So, here we use set builder form.