The One-Pass Announcement: Binding Times to the Right Noun
On Tuesday, a class listens once to a 90-second campus announcement containing two changes. First, because of road repairs, the 4:40 p.m. shuttle from North Gate is cancelled; replacement buses leave from East Gate at 4:50 and 5:10, and the last replacement bus is at 6:10. Normal North Gate service resumes the next day. Second, the library workshop "Finding Sources for First-Year Papers" moves from Room 204 to the Media Lab on the third floor. It runs 4:30-5:15, and students should arrive ten minutes early to sign in; the sign-in sheet is what counts for attendance credit. The student listening works at a cafe with a 5:30 p.m. start. The cafe is a 12-minute walk from the library, and the time clock closes at 5:25. The student's notes read: "shuttle 4:40? East Gate 4:50 and 5:10; workshop 3F Media Lab 4:30-5:15; shift 5:30." A classmate says, "Just take the 5:10 bus and leave the workshop early - it's the same thing."
1. The notes contain one recorded number that is easy to attach to the wrong event, and one missing constraint that decides the whole evening. Identify both and explain how a single listening pass produces this error.
Read the worked answer
Wrong binding: "5:10" belongs to the replacement bus from East Gate, not to the workshop or the shift. Under time pressure the brain stores the number and drops the noun it was attached to, so "5:10" floats free and can be misread as a workshop time or a departure the student can use.
Missing constraint: the 4:20 sign-in (ten minutes before 4:30). The notes capture the workshop's start and end but not the arrival deadline, which is the only detail that determines whether attendance credit is earned.
A single pass is enough only for gist; exact times need a second check. The reliable note would read: "Bus: East Gate only, 4:50 / 5:10 / last 6:10. Workshop: Media Lab 3F, sign in 4:20, 4:30-5:15." Separating "place + time" pairs prevents the drift.
2. Using the times given, decide whether the student can sign in, stay to the end, and reach the cafe by 5:25. Show every step, and evaluate the classmate's advice.
Read the worked answer
Sign-in 4:20 → workshop 4:30-5:15 → 12-minute walk → arrival 5:27. The clock closes at 5:25, so the student is 2 minutes late if they stay to the end.
Options, in order of cost:
- Leave at 5:13, two minutes early. Sign-in already happened, so attendance credit is secure; only the closing remarks are missed.
- Ask the cafe to move the start to 5:35. Cheapest if the manager agrees.
- Skip the workshop. Worst, because the credit is lost.
The classmate's advice fails on logic: the 5:10 bus leaves before the workshop ends and has nothing to do with reaching a cafe 12 minutes' walk away. The bus solves a trip home, not the shift. "Same thing" hides two different problems - transport and punctuality - and only the second one is real here.
3. Write the single question the student should ask the workshop organizer, and explain why that question matters more than the others.
Read the worked answer
"If I sign in at 4:20 but leave at 5:13, do I still get attendance credit?"
Why this one: the announcement says the sign-in sheet "counts for attendance credit," which implies credit is earned at the start, not at the end - but it never says so explicitly. The student's binding risk is credit, not content. A question about handouts or slides is low value because those can be borrowed. A question about the bus is irrelevant because the bus does not affect the shift. One precise question about the rule that governs the outcome is worth more than three about logistics.