From the archive, Friday 21 August 2026
Math Review, 1 of 5, Units, Notation, and Rearranging
Today is about the two habits that make the rest of the year easier: rearrange the equation before you touch a number, and carry your units through every line. Three questions, each one harder than the last. You unlock the next one by answering the one you are on.
Level 1: PhD dropout
A rectangular solar panel measures 4.20 m by 3.15 m. Give its area in cm2, to the right number of significant figures.
About 2 minutes. Watch out for the area conversion, which is where almost everyone loses this one.
Levels 2 and 3
Level 2, CalTech, opens once you have cleared Level 1, and it comes with every hint. Level 3, Lucasian, needs a class code. Nothing on an archived day is recorded, and nothing counts toward a leaderboard.
The interactive version of this day, with the tutor and the calculus companions, loads here when your browser runs the page script. See also today’s question and the rest of the archive.