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Short guides with formulas and worked examples. A guide links to practice questions when a matching topic is available.
- How to calculate molarityMolarity is the number of moles of solute per litre of solution. Here is the formula, a worked example, and a shortcut for solving molarity problems quickly.
- How to balance a chemical equationBalancing chemical equations means making the same number of each atom appear on both sides. Learn the steps with a worked example.
- How to convert fractions to decimalsDivide the numerator by the denominator to turn any fraction into a decimal. Here is the method, including what to do with repeating decimals.
- How to read a weather mapWeather maps use symbols for pressure centres, fronts, and precipitation. Here is how to decode the letters, lines, and colours on a synoptic chart.
- How to calculate years between historical datesBCE and CE dates meet at year 1 — there is no year 0. Here is how to count the years between events across the eras.
- The path of blood through the heartOxygen-poor blood enters the right side, gets re-oxygenated in the lungs, and oxygen-rich blood leaves the left side. Follow the complete loop.
- How to read a Punnett squareA Punnett square shows every possible combination of parental alleles. Learn to compute genotype and phenotype probabilities in monohybrid crosses.
- How to apply the 10% rule in food chainsEnergy moves between trophic levels, but only about 10% transfers upward. Here is how to compute energy at each level of a food chain.
- How to trace Python code by handTracing means predicting exactly what a program prints. Learn the discipline: track variables, follow loops, and evaluate expressions in order.
- How to use Big-O notationBig-O describes how runtime grows with input size. Learn to recognise O(1), O(log n), O(n), and O(n²) in common algorithms.
- Česká chemická nomenklatura — oxidační čísla a názvoslovíPro české uživatele: jak české názvosloví odvozuje názvy sloučenin, kyselin a solí z oxidačního čísla. Přehled koncovek pro oxidační čísla I–VIII, odborná terminologie a příklady.