Which note value lasts for 1½ beats?

The note value that lasts for 1½ beats is a dotted crotchet. A dotted crotchet consists of a regular crotchet (which is worth 1 beat) combined with a dot that increases its duration by half its value, which is an additional half beat. Therefore, adding the 1 beat from the crotchet and the 0.5 beats from the dot gives a total of 1½ beats.

In contrast, a quaver is worth half a beat, a crotchet is worth 1 beat, and a dotted quaver spans 1½ beats, but it does so differently, as it has a quaver plus a dot, leading to a different context for beats. Thus, the dotted crotchet is specifically the note that accurately lasts for the desired duration of 1½ beats.