Modals of deduction and possibility worksheets
50 worksheets and 2 lessons · Modals & verb patterns
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Modals of deduction & possibility worksheets
50 printable worksheets with answer keys; the 24 most used, easiest level first.
Modals of deduction & possibility lessons
2 ready lessons for the four skills: teach on the board, set online or print.
Warm-ups and fillers
Quick Fun Corner activities on the same theme: no preparation.
- Filler · B2Describe a scene: “On my desk this morning: a wet umbrella, half a pizza and a note that says ‘Sorry!’” Students deduce: “Someone must have eaten your pizza.” “It can’t have been the cleaner.”
About Modals of deduction & possibility
Modals of deduction show how certain we are. Must means we are almost sure something is true (She must be tired – she's worked all day), can't means we are sure it isn't (That can't be John – he's in Spain), and might, may and could express possibility: It might rain later. For the past we add have + past participle: He must have missed the bus.
Present deduction is usually taught at B1 and past forms at B2, with refinement at C1. Learners typically use mustn't as the opposite of must (*It mustn't be true instead of It can't be true), use can for a specific possibility (*It can be John instead of It could be John), and struggle to hear the weak forms must've and might've.
This page offers printable modals of deduction worksheets with answer keys, which can be printed as PDFs or completed online via a class link.
Teaching tips: Modals of deduction & possibility
- Use mystery pictures or a 'What's in the bag?' task so learners speculate with must, might and can't.
- Place the modals on a certainty line, from can't at one end through might, could and may to must at the other.
- Detective stories work well for past deduction: The thief must have had a key.
- Watch for mustn't in negative deduction; the opposite of must be in this sense is can't be.
- Drill the weak forms must've, might've and can't have so learners recognize them in fast speech.
Questions teachers ask
What's the difference between must and can't in deduction?
Must means I'm sure this is true; can't means I'm sure it isn't true. Mustn't is not normally used for negative deduction.
Are may, might and could interchangeable?
For present and future possibility they are very close: It may, might or could be true. In the negative they differ: may not and might not express possibility, but couldn't expresses near-certainty that something is impossible: It couldn't be him.
How do I teach past modals of deduction?
Start from a clear situation (the grass is wet this morning), elicit present deduction, then move to the past: It must have rained. Highlight the form modal + have + past participle.