The Broken Vending Machine
A campus notice board displays this sign: 'Due to a fault, the vending machine in Block C will not accept coins until it has been repaired. Students who have already inserted coins and received no item should report to the front desk, where a refund will be given only if a receipt is produced. The machine will be out of service on Tuesday and Thursday mornings.' A student reads the sign and says: 'So I can still use notes, and I can get a refund without a receipt if I complain loudly.' Another student says: 'The sign says the machine is completely broken all week.'
1. Identify precisely what the sign does and does not state, and correct both students' readings.
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What the sign states:
- Coins are not accepted until repaired - it says nothing about notes, so notes are not ruled out, but they are also not confirmed as working. The sign is silent, not permissive.
- A refund requires a receipt. There is no exception for complaining.
- The machine is out of service on Tuesday and Thursday mornings only - not all week.
Corrections:
- Student 1 is wrong on both counts. The sign does not say notes work (silence ≠ permission), and it explicitly conditions refunds on a receipt.
- Student 2 is wrong: 'out of service on Tuesday and Thursday mornings' is a limited window, not 'completely broken all week.'
The lesson is that a careful reader distinguishes what is stated, what is implied, and what is merely not forbidden.
2. Rewrite the sign in two or three sentences so that it is unambiguous about coins, notes, refunds, and the out-of-service window.
Read the worked answer
Model rewrite:
'The Block C vending machine is faulty: it will not accept coins until further notice. Note acceptance is untested and should not be relied on. If you inserted coins and received no item, take your receipt to the front desk for a refund - refunds cannot be issued without a receipt. The machine will be out of service on Tuesday and Thursday mornings.'
Why this is better:
- It replaces 'until it has been repaired' with 'until further notice' (clearer about duration).
- It explicitly addresses notes instead of leaving silence that could be misread as permission.
- It keeps the receipt condition but states the consequence ('cannot be issued') so it is not mistaken for a suggestion.
- It preserves the exact out-of-service window so nobody infers a full-week outage.