Enter a number between 1 and 100 and press the "Guess" button.
Is your number ?
Type a number, "odd", "even", "prime", or "divisible by " a number. Then press [ENTER] or click on the "Guess" button.

This is a heavily modified version of a simple guessing game. Beginning students will likely stick with numbers. But show them that it is more efficient to guess midpoints within a range of choices. For example, for a number in the range 30 to 50, guessing 40 is usually more efficient than guessing 35. Guessing 35 may result in the elimination of only 5 numbers (30 to 35), but guessing 40 will definitely result in eliminating 10 (the ten above or below 40).

As they gain experience with the game, encourage students to use some of the available alternative guesses. By allowing more types of clues, more critical thinking is engaged. It allows them to practice divisibility rules and other number characteristics.