Your teacher has gone to a staff briefing. Staff briefings last forty minutes. They have never, in the history of this school, finished early.
Roughly 35–40 minutes. Designed for one device per group of three or four. Every wrong code costs 60 seconds, so guessing is punished — that is deliberate.
| Lock | What it needs | Answer | Where the difficulty is |
|---|---|---|---|
| The drawer | Five constraints across three notes; construct a 3-digit number | 432 | There is no candidate list. They must reason from "first digit is double the last" and parity to fix the units digit, then use the digit sum |
| The chair | Two bounds over a discrete set. ¾ of 52 fixes the floor, ¾ of 60 fixes the ceiling, and the lift locks at only five heights | 42 cm | Four notes, none sufficient alone, and the upper bound is itself a two-step chain. One bound alone leaves three candidate notches and no way to choose |
| The clock | Angles on a straight line to get x, then a clock-angle | 2:30 | Two-stage: derive x = 105° from the whiteboard, then realise the hour hand moves. 120° is the near-miss |
| Your padlock | Find both missing constants, then solve the equation | 1729 | The equation is unusable until the bookshelf and the trophy have both been searched |
Each act has three hints: a nudge, then the method, then the answer. Taking hints costs nothing — only wrong codes cost time. 1729 is the taxicab number, the smallest number expressible as the sum of two cubes in two different ways (1³+12³ and 9³+10³). There is a good five-minute Ramanujan story in it if you want one for the debrief.
Nothing tells you which note belongs to which lock. That is the job.
Sir / Miss — your chocolate is in the drawer.
The padlock code is the value of x.
Take your time. We'll wait.