The short version Geometry terms build on each other. Kids learn shapes and their parts in K to 2, then lines, angles, area, and perimeter in grades 3 to 5, then circles, angle pairs, transformations, and the Pythagorean theorem in grades 6 to 8. The glossary tables below list the key geometry vocabulary for each…
The short version Numbers 1 to 20 each have their own word and have to be memorized. Watch fourteen, fifteen, and eighteen (one t). The tens are twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety. Forty has no u. Ninety keeps the e. For 21 to 99, write the tens word, a hyphen, then the…
The short version The least common multiple (LCM) of two numbers is the smallest number both of them divide into evenly. The LCM of 3 and 9 is 9, and the LCM of 4 and 6 is 12. For small numbers, list the multiples of each and stop at the first one they share. For…
The short version The greatest common factor (GCF) is the biggest number that divides evenly into every number in the group. The GCF of 4 and 6 is 2. For small numbers, list all the factors of each number and pick the biggest one they share. For bigger numbers, use prime factorization and multiply the…
The short version Prime factorization means writing a number as a product of prime numbers only. For example, 60 = 2 × 2 × 3 × 5, or 2² × 3 × 5. Prime factors are the prime numbers that multiply together to make the original number. The prime factors of 60 are 2, 3,…
The short version Surface area is the total area of every outside face of a 3D shape. Find the area of each face, then add them all up. Cube: 6 × side². Rectangular prism: 2lw + 2lh + 2wh. Cylinder: 2πr² + 2πrh. Square pyramid: the base area plus four triangles, or s² + 2sl,…
The short version A square root of a number is a value that, multiplied by itself, gives that number. The square root of 49 is 7, because 7 × 7 = 49. The square root of a square undoes the squaring: √(6²) = √36 = 6. With variables, √(x²) = |x|, since the answer can’t…
The short version Two step equations take two inverse operations to solve, like 3x + 7 = 22. Undo the adding or subtracting first, then undo the multiplying or dividing. Here, subtract 7 to get 3x = 15, then divide by 3 to get x = 5. The do undo method: list what was done…
The short version To go from slope intercept form (y = mx + b) to standard form (Ax + By = C), move the x term to the left side so x and y sit together and the constant sits alone on the right. If the slope or intercept has fractions or decimals, multiply every…
The short version A tessellation is a pattern of shapes that covers a flat surface with no gaps and no overlaps, and it can keep going forever in every direction. Only three regular polygons tessellate by themselves: equilateral triangles, squares and regular hexagons. The reason is angles. The corners meeting at any point have to…