Question

Which of the following is an irrational number?

Options

• `sqrt(4/9)`

• `sqrt(12)/sqrt(3)`

• `sqrt(5)`

• `sqrt(81)`

Answer 1

`bb(sqrt(5))`

Explanation:

Let’s analyse each:

a. `sqrt(4/9) = sqrt(4)/sqrt(9) = 2/3`, which is a rational number.

b. `sqrt(12)/sqrt(3) = sqrt(12/3) = sqrt{4} = 2`, also rational.

c. `sqrt(5)` is an irrational number because 5 is not a perfect square.

d. `sqrt(81) = 9`, a rational number.

Therefore, the irrational number is `sqrt(5)`.