Short interactive lessons that ask a question before they explain. One session takes about ten minutes and ends with questions to check what you have understood.
A model keeps the few quantities that decide the answer to one question and leaves out the rest, on purpose.
Class 9 · Science How Science Works FreeWords such as work have exact meanings in science, and an equation states how quantities are related.
Class 9 · Science How Science Works FreeA measurement is a number and a unit. One airliner ran out of fuel because pounds were used in place of kilograms.
Class 9 · Science How Science Works FreeA law describes a pattern, a theory explains it, and a principle applies across many situations.
Class 9 · Science How Science Works FreeA prediction is an expected result worked out from evidence. A claim is testable when it names something measurable.
Class 9 · Science How Science Works FreeRough values of each quantity give an answer of the right size, good enough to check a calculation.
Class 9 · Maths Coordinates FreeOne number fixes a point on a line; a point in a plane needs two, measured along perpendicular axes.
Class 9 · Maths Coordinates FreeThe axes, the origin and the ordered pair (x, y). The x-coordinate is the distance from the y-axis.
Class 9 · Maths Coordinates FreeFour quadrants, four sign patterns. (3, 5) and (5, 3) are different points, and reflection changes one sign.
Class 9 · Maths Coordinates FreeThe coordinate differences are the legs of a right triangle, and the Baudhayana-Pythagoras theorem gives the distance.
Class 9 · Maths Coordinates FreeThe midpoint is the average of the coordinates. The same idea finds a missing endpoint and the trisection points.
Class 9 · Maths Coordinates FreeWidths, overlaps of circles and collinearity, all calculated from coordinates on floor plans, grids and screens.
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