Classroom mode
Run it in class
In a room of 30 kids, what are the odds two of them share a birthday?
Show of hands — before you project anything
Predict first: by a 30-person room, which question has crossed one-half—or has neither?
- A Way more than you'd guess
- B About what you'd guess
- C Way less than you'd guess
Count the votes out loud. Hold them to it — then watch.
Project it (fullscreen)
Discussion prompts
- Predict first: by a 30-person room, which question has crossed one-half—or has neither?
- Why does the chosen-person model add one spoke while the all-pair model adds several links?
- How would fewer possible dates change the no-match calculation?
Where it shows up in real life
- A classroom or sports team comparing one person's birthday with every pair
- A party where people discover a birthday twin without planning it
- Matching first initials, favorite colors, or other labels inside a group
A prediction-first worksheet — no answer key.
zero prep · no login · any projector
Winding down at home? Family mode ·
Explore every question
In a room of 30 kids, what are the odds two of them share a birthday?
Predict — what do you think will happen, and why?
Talk about it
- Predict first: by a 30-person room, which question has crossed one-half—or has neither?
- Why does the chosen-person model add one spoke while the all-pair model adds several links?
- How would fewer possible dates change the no-match calculation?