Friday Fave for October 19

  • The personified Friday Fave is a figment of the imagination.
  • The Friday Fave posts every Friday without fail.
  • The Friday Fave seeks to help you, Dear Reader, find new and wonderful things for your students.

Two of these statements are true, and one is a lie.

When the truths and lies are about people or fictional constructs, you can’t really know which is a lie unless you know the person or construct very very well.

But mathematical truths and lies are different. The evidence for veracity or mendacity is right there in the math. If you don’t know it, you can figure it out! This makes Two Truths and a Lie fertile ground for mathematical concept development; especially if

For months, Desmos has had some secret-not-ready-for-public-use Two Truths and a Lie activities, and now we’ve polished several of these and put them on display in the searchable activities at


We have versions of this activity for each of these function types: Conics, Exponentials, Parabolas, and Linears (all true; no lies!). They are Challenge Creator based, so the differentiation is built right in—your students are telling the truths and the lies, as well as determining exactly which conic (or exponential or line) they’ll lie about.

The Friday Fave (who missed last week’s post, and so now you know the lie) encourages you to click on through and give these Two Truths and Lie activities a try.