Unit 1 · The Number System & Roots

Approximating Irrational Roots

Trap a square root between consecutive integers, then refine with decimals.

Grade 8 State Test
NY-8.NS.2NY-8.EE.2

Notes

Squeeze theorem for Grade 8

To estimate √40, note 6² = 36 and 7² = 49. So 6 < √40 < 7. Since 40 is closer to 36 than to 49, √40 is a little more than 6.3.

Vocabulary

perfect square

An integer that is the square of an integer.

Example: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100.

Worked examples

Try the prompt first. The steps stay folded until you ask to see them.

Between which two integers?

Between which two consecutive integers is √70?

Common errors

Watch for

Using (n/2)² instead of nearby perfect squares

Estimation needs the closest integer squares, not half the number.

Fix: Memorize perfect squares through 15² = 225.

Explore with an applet

Guided practice

Submit each answer to check it. The key is not shown until you do.

Question 1 of 3Grade 8 State TestNY-8.EE.2Grade 8 Mathematics · Spring 2024 · Q40Calculator permittedemerging

The area of a square-shaped garden is 324 square feet. What is the length, in feet, of each side of the garden?

Choose or type an answer first. The key stays hidden until you do.
Question 2 of 3Grade 8 State TestNY-8.EE.2Grade 8 Mathematics · Spring 2023 · Q39Non-calculatoremerging

What is the solution for x in the equation x³ = 125?

Choose or type an answer first. The key stays hidden until you do.
Question 3 of 3Grade 8 State TestNY-8.EE.2Grade 8 Mathematics · Spring 2024 · Q40Calculator permittedemerging

The area of a square-shaped garden is 324 square feet. What is the length, in feet, of each side of the garden?

Choose or type an answer first. The key stays hidden until you do.

Intervention

Build a perfect-square flash ladder from 1² through 12².

Enrichment

Estimate ∛30 using 3³ = 27 and 4³ = 64.

Explain your reasoning

Sentence starters · Notice and Wonder · Three Reads · Think-Pair-Share · Compare and Connect · Math Talk · Stronger and Clearer Each Time

  • √n is between … because …