Two coins add up to 30 cents
Published , last checked . Re-solved cold against the published wording before it went live: how puzzles and answers are checked.
A short money riddle that trips people who assume both coins are normal. From the free puzzle set on Think Fanny. Next try What has a neck but no head?.

Coin denominations, from the mint
The answer only holds with United States coin values, so here they are from the people who strike them and from two neutral write-ups:
If one of these contradicts the answer above, we would rather hear it than not. See how puzzles and answers are checked.