Loading the interactive

How can a tusk tell time?

Algebra 2Exponential decayabout 2 minCCSS HSF.LE.A.1.cCCSS HSF.LE.B.5

Read a mammoth tusk's carbon clock, one half-life at a time.

Lesson Plan

Explore exponential decay and half-life, the basis of radiocarbon dating.

  1. Question: Ask what students spot and what they are curious about. Read “After one more half-life, how much is left?” aloud. Have each student guess and say why.

  2. Question: Read “Could this clock tell the age of a dinosaur?” aloud. Have partners explain their guesses to each other.

  3. Real-world application: Ask: Where else have you seen this?

  4. Your turn: Have students try their own. Ask them to predict before they test.

How to run it

  1. Whole classPut the lesson on the board. At each choice the class votes, then you select the winner.
  2. SoloShare the link, QR code, or post to Google Classroom. Each student gets to take their own path.