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The short version A composite number is a whole number greater than 1 that has more than two factors. In other words, something besides 1 and itself divides into it evenly. The first composite numbers are 4, 6, 8, 9, 10, 12, 14 and 15. The smallest is 4. 1 is neither prime nor composite….
The short version Pi is irrational. It can’t be written as a fraction of two whole numbers, and its decimal never ends and never repeats. 22/7 and 3.14 are rational numbers that sit close to pi. They’re handy approximations, but neither one equals pi. Pi = circumference ÷ diameter looks like a fraction, but for…
The short version Like terms have the exact same variable part: same letters raised to the same powers. 4x and -9x are like terms. 4x and 4x² aren’t. To combine like terms, add or subtract the numbers in front (the coefficients) and keep the variable part unchanged: 3x + 5x = 8x. The sign in…
The short version A quadratic function is any function that can be written as f(x) = ax² + bx + c, where a isn’t zero. The highest power of x is 2. Its graph is a U-shaped curve called a parabola. It opens up when a is positive and down when a is negative. The…
The short version Flat shapes with straight sides are polygons, and they’re named by how many sides they have: triangle (3), quadrilateral (4), pentagon (5), hexagon (6), heptagon (7), octagon (8), nonagon (9), decagon (10). Most polygon names are a Greek number plus “gon,” which means angle. So a pentagon is literally “five angles.” Triangles…
The short version A mixed number is a whole number and a proper fraction written together, like 3 1/2. It means 3 + 1/2. To turn a mixed number into an improper fraction, multiply the whole number by the denominator, add the numerator, and keep the denominator: 3 1/2 = 7/2. To go back, divide:…
The short version Vertical means up and down, like a flagpole or a standing person. Horizontal means side to side, like the horizon or a person lying in bed. Memory trick: horizontal starts like horizon, the flat line where the sky meets the ground. On a graph, the x-axis is horizontal and the y-axis is…
The short version A prism is a 3D shape with two identical, parallel polygon faces (the bases) joined by flat rectangular sides. The shape of the base gives the prism its name. A rectangular prism has 6 faces, 12 edges and 8 vertices. A triangular prism has 5 faces, 9 edges and 6 vertices. For…
The short version If the divisor (the number you divide by) is a whole number, divide normally and put the decimal point in the answer directly above the one in the dividend. If the divisor is a decimal, move its decimal point right until it’s a whole number, then move the dividend’s decimal point right…
The short version A decimal is a number written with a decimal point, where the digits to the right of the point stand for parts of a whole: tenths, hundredths, thousandths and so on. 0.7 means 7 tenths (7/10). 0.07 means 7 hundredths (7/100). Each place to the right is worth one tenth of the…