Grade 8 · Unit 1Topic 3 of 3~22 min

Roots & Irrational Numbers

Evaluate square and cube roots and tell rational from irrational numbers.

Step 1 · Learn

Walkthrough

Read this first — it covers the idea in plain language with a worked example.

The square root of 49 is 7 because 7 × 7 = 49. The cube root of 8 is 2 because 2 × 2 × 2 = 8.

Rational numbers can be written as a fraction; their decimals end or repeat (like 0.5 or 0.333…).
Irrational numbers cannot; their decimals go on forever without repeating (like π or √2).

Tip

The square root of a perfect square (4, 9, 16, 25…) is rational. Most other square roots are irrational.

Step 2 · Watch

A short video that walks through this topic.

Khan Academy

What the radical symbol means and how to find square roots.

Step 3 · Practice

Try a worksheet or work through some problems before the quiz.

Step 4 · Check

A couple of questions to make sure this topic stuck. Retake as many times as you want.

Roots & Irrational Numbers

Easy

What is √64?