We created the Web Sketchpad game below (and here) as part of our Dynamic Number project. It challenges elementary-age students to uncover the value of a secret number by collecting and analyzing clues that narrow its range of possible values. The game familiarizes students with inequality signs, introduces the use of x to represent an unknown value, and motivates students to develop strategies for finding the secret number in as few guesses as necessary.
There are seven variants of the game. Use the arrows in the lower-right corner of the game to move from one version to the next.
The video below the game provides a short introduction to the game.
An annotated list of all our elementary-themed blog posts is here.