Guess the Date

This is an activity for the classroom that I think illustrates a brute force attack.




The teacher thinks of a date. The students have to guess the date. The students are allowed to ask questions but the teacher is only allowed to answer yes or now.


Typical example should go something like this.

Teacher: I’m thinking of a date.
Student: Is it after July 1st?
Teacher: Yes.
Student: Is it in July?
Teacher: No.
Student: Is it in August.
Teacher: No.
Student: September?
Teacher: No.
Student: October.
Teacher: Yes.
Student: Is it in the first half of the month?
Teacher: Yes.
Student: Is it the 1st?
Teacher: No.
Student: 2nd?
Teacher: No.
Student: 3rd?
Teacher: No.
Student: 4th?
Teacher: Yes. The date was October 4th.


This is an example of how a brute force attack works. The attacker gets what information they can to narrow the field then starts with rapid fire guessing, is it 1? 2? 3? 4? 5?. This technique is pretty commonly used still but isn’t very efficient, and the less information you have to start with the longer it will take over all.


Make sure you don’t think of a date that the students will guess quickly, like the first of January, or any month for that matter. Also avoid the end of the month, otherwise you’ll be there all day. Sticking in the region of ¬†4th – 10th should usually suffice.

You don’t actually have to think of a date, just answer the questions in a manner that will bring out the pattern to illustrate the point. Once you think the point has been illustrated, just tell them they’re correct.