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Knowledge base
More explainers from the knowledge base. Each one names what you need to know first, works through the method, and says where it usually goes wrong.
Concept CalculusWhat Is an Integral? A Plain ExplanationAn integral runs a rate of change backward to recover the original quantity, or adds up an infinite number of infinitely thin slices to measure an area. Both descriptions turn out to be the same idea.
Method StatisticsHow to Find Mean, Median and ModeThree short procedures. The only one with a trap is the median, and the trap is forgetting to sort.
Concept StatisticsWhat Is an Average? Three Different AnswersAn average is a single number standing in for a whole set. There are three because there are three reasonable ways to choose it.
Method GeometryHow to Use the Pythagorean TheoremThree steps, and the only decision is whether the side you want is the hypotenuse or one of the legs.
Concept Pre-AlgebraWhat Is a Proportion? Two Equal RatiosA ratio compares two quantities. A proportion claims two ratios are the same — and that claim is what you can solve.
Mistakes Converters5 Temperature Conversion MistakesEvery one of these is caught by one sanity check: does the answer land where you would expect it to on a weather forecast?