The Root Hunter

Some numbers can't be caught — but they can be trapped. Build fences on the number line, squeeze them ten times tighter with every zoom, and discover which numbers never stop running.

Grade 8 · Unit 2 8.NS.1 Rational vs. irrational 8.NS.2 Rational approximations 8.EE.2 Square & cube roots
Part 1

The Fence Hunt

Your target hides on the number line. Place a fence: if its square is at most the target's radicand, and the next fence's square is past it, the target is trapped between them. Trap it, zoom in ×10, and trap it again — one decimal digit per zoom.

√7 = ?
Zoom level 1 of 3 — whole numbers. Pick the fence just below your target.
Part 2

Decimal Detective

A number is about to reveal its decimal expansion. Lock in your prediction first: will the digits terminate, repeat forever, or never settle at all? Then the reveal shows the expansion — and the reason.

Case 1 of 5
3/8
Part 3

The Root Machines

Three machines that turn Part 1's discoveries into airtight moves: convert any repeating decimal to a fraction, undo squares and cubes, and shrink a trap forever.

Every repeating decimal hides a fraction. The machine proves it with algebra: name it x, shift it, subtract, solve.

Squaring and cubing are actions — roots undo them. Solve x² = p and x³ = p, then classify the answer.

The Fence Hunt, industrialized. Every press tightens the trap by a factor of ten — and the target still never gets caught exactly.

TrapLower fence²Upper fence²Trap width
Part 4

The Hunter's Exam

Ten questions. Wrong answers get a hint that names the exact machine or hunt move that proves the right idea.

📦 Word Box

Rational number
A number that can be written as a fraction of two integers. Its decimal form terminates or repeats.
Irrational number
A number that cannot be written as a fraction of integers. Its decimal form never terminates and never repeats.
Square root (√)
The number that, multiplied by itself, gives the radicand: √49 = 7 because 7 × 7 = 49.
Cube root (∛)
The number that, used as a factor three times, gives the radicand: ∛64 = 4 because 4 × 4 × 4 = 64.
Radicand
The number under the root symbol — the target's hiding spot in the Fence Hunt.
Perfect square
A whole number that is some integer squared: 1, 4, 9, 16, 25, … Its square root is rational.
Perfect cube
A whole number that is some integer cubed: 1, 8, 27, 64, 125, … Its cube root is rational.
Terminating decimal
A decimal that ends: 3/8 = 0.375.
Repeating decimal
A decimal whose digits fall into a cycle forever: 5/11 = 0.454545…
Bar notation
The bar marks the repeating block: 0.4̄5̄ means 0.454545…
Successive approximation
Trapping a number between rationals, then tightening the trap by another power of ten — the Fence Hunt's whole strategy.
Real number line
Home of every rational and irrational number. The irrationals fill the gaps the fractions leave behind.