Mixed set
Heights and times of tide
Four procedures that all end in a depth or a clock time; the marks are lost picking the wrong one.
Drawn across the whole group, leaning towards the topics you get wrong most, as far as the questions written for those topics allow. Expect it to feel harder than a single-topic drill — that difficulty is what makes it stick. Every visit draws a different set.
Dealing your set
Rather take them one topic at a time? All topic drills.