Work through the levels in order. Type your answer and press Check — open the worked solution if you get stuck. Answers like -6, 3/4 or 0.25 are typed exactly as shown.
Level 1 · Warm-up
1 What is the minimum useful exercise dose given in this lesson?
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A 20–30 minute walk, 3–4× a week. Better and ideal doses build from there.
2 Roughly how little dehydration is enough to reduce cognitive performance?
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2% — small enough to arrive before you feel thirsty.
Level 2 · Core
3 When is the best time to take a 15–20 minute walk if you want to help a study session?
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Just before starting — you study inside the 2–4 hour window of elevated function. (Exercise after study also helps consolidation.)
4 Why does the lesson call the physical basics a "hierarchy of needs"?
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Thinking is built on top of sleep, food, water and comfort. Unmet basics cap what any study technique can achieve.
Level 3 · Challenge
5 A student studies badly all afternoon and concludes "I am just bad at chemistry." What should they check first?
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Run the physical checklist. On most bad study days at least one box is a "no" — a far cheaper fix than a change of subject.
6 Why does caffeine after 2pm harm today's study, not just tonight's sleep?
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Sleep consolidates today's learning. A late stimulant degrades that night — so today's study never gets properly filed.