Play it · Ages 10–11
The Hundred Lockers
Which doors are left open? Three challenges — each one changes what you have to do, not just how many of it there are. Nothing is timed and nothing is scored.
0 of 3 solved
Run the students and watch which lockers end up open.
Small enough to follow by eye. Say what the open ones have in common.
Twenty lockers
How many of the 20 lockers will be left open?
Ten minutes of stuck counts as the work.
Now do it away from the screen
The board is the warm-up. The year page has the same problem on paper, the hint ladder, the answer, the five-day week and three questions nobody can mark — which is where the twenty-five minutes actually go.