4th Grade · Ages 9–10
The Three-Answer Year
Nine is old enough to be told that a question has a size — and that you can work out whether a plan can possibly work before you try it.
- 1 Hard Thing
- 5 days · 105 minutes
- 3 unmarkable questions
Ready?
4th Grade · Eight Coins, One Light
Nine is old enough to be told that a question has a size — and that you can work out whether a plan can possibly work before you try it.
Full screen — no distractions
Where this goes
The ladder
The same idea, three times, roughly a year apart. This is what depth looks like from the outside.
This year
Eight coins, fake known to be lighter.
Next year
Twelve coins where you do not know whether the fake is heavy or light. The same counting argument says three weighings, and it is right.
The year after
The idea underneath: information has a size, and you can measure it before you have the answer.
What lives on the desk this year
- A balance you built yourself
- Identical coins and one that is not
- Paper wide enough for an outcome tree
- A stopwatch
- A wall for the things you got wrong
The rest of 4th Grade
One hard thing a day is the sharp end. It sits on top of an ordinary year.
Last updated: September 2026