Statement: If p, then q
Inverse: If q, then p
Converse: If not p, then not q
Contrapositive: If not q, then not p.
We can see from the statement that p = brush teeth twice a day and q = not get cavities.
Thus:
Inverse: If I don't get cavities, then I brush my teeth twice a day. FALSE (for example, I might floss extra well instead. Brushing my teeth twice a day is not the only way to avoid cavities)
Converse: If I don't brush my teeth twice a day, then I get cavities. FALSE (for example, I might not eat a lot of sugar and thus I don't get cavities)
Contrapositive: If I get cavities, then I did not brush my teeth twice a day. TRUE
If this confuses you, try the example of p = cat and q = four legs. (i.e. the statement is If this is a cat, it has four legs). Try making the inverse, converse, and contrapositive, and see the truth of those statements.
