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Math · 7th Grade
Area of a Circle
Square the radius, never the diameter.
How to use it
Write r = … before anything else. Halving the diameter is the step people skip.
Free · print-ready PDF · US Letter and A4
- Grade
- 7th Grade
- Ages
- 12–13
- Subject
- Math
- Pages
- 1
The rest of the 7th Grade wall
49 more posters, all free to print — 11 of them here.
Solving ProportionsTwo equal ratios, and the cross-multiplication that solves them.Constant of ProportionalityThe single number that turns one quantity into the other, every time.Percent Increase and DecreaseChange over original — and why the original is always the bottom.Tax, Tip and DiscountThree names for the same multiplication.Operations with Rational NumbersNegative fractions and decimals — convert to one form, then apply the sign rule.Two-Step EquationsUndo in reverse order: plus and minus first, then times and divide.Variables on Both SidesCollect the letters on one side and the numbers on the other.Circumference of a CircleThe distance around, and the two formulas that are the same formula.Angle PairsFive relationships that let you find a missing angle without measuring.ProbabilityA number between 0 and 1 — and what it does and does not promise.Probability of Two EventsMultiply for 'and', add for 'or' — once you have checked they cannot overlap.