Students meet pi (π) — the special number connecting a circle’s distance around to its distance across — and use it to find any circle’s circumference (πd) and area (πr²).
Students will be able to…
Every circle in the universe shares one magic number: its distance around divided by its distance across is always about 3.14. Why — and how do we use it?
Project this and change the radius. Watch the circumference and area update, and see how each is built from the radius using π.
Tap any phase to open the teacher moves and student actions.
Distance around ÷ distance across — always the same?
Teacher models.
Class drives the Circle Tool.
Students find C and A.
One circle.
Aligned to the Common Core State Standards for Mathematics, including the Standards for Mathematical Practice.
Know and use the formulas for the area and circumference of a circle.
Solve problems involving area, volume, and surface area.
Solve problems involving scale drawings of geometric figures.
Look for and make use of structure in circle formulas.
Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.
Have students wrap string around round objects to measure circumference, measure the diameter, and divide to discover π for themselves. A printable circle-lab sheet is in the Math library.
Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.
A quick self-check with instant feedback, drawn from this lesson’s key terms.
A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.