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 Algebra 1 Numbers Operations Ratios and proportions Percents Measurement Geometry Perimeter Perimeter: find the missing side Area Volume Surface Area Similar figures: side lengths and angle measures Similar triangles and indirect measurement Dilations Perimeter and area of similar figures Area between two shapes Similar Solids Perimeter, area, and volume: changes in scale Pythagorean Theorem Coordinate Graphs Variable expressions and equations Solve Equations Single-variable inequalities Absolute value equations and inequalities Matrices Data and graphs Algebra 2 Arithmetics Divisibility Decimals Fractions Exponents Proportional reasoning Radical expressions Graphs Monomials Polynomials Factoring Variable expressions Linear Equations Linear Functions Graphs of linear equations Inequalities Quadratic equations Graphs of quadratic equations Absolute Value Radical expressions Exponential equations Logarithmic equations System of equations Graphs and functions Plotting points and naming quadrants Interpreting Graphs Relations and Functions Function Notation Writing a Linear Equation from a Table Writing a Linear Equation to describe a Graph Direct Variation Indirect Variation Domain and range Sequences and series Matrices Inverse of a matrix Determinants Inner product Geometry Triangles Quadrilaterals Points, lines, and segments Angles Lines in the coordinate plane Polygons 2-D Figures 3-D Figures Areas Surface Area Volume Pythagorean Theorem Building Blocks Geometry Transformations Parallel, coincident and intersepting lines Distances in the plane Lines in space Plane in space Angles in the space Distances in the space Similarity Precalculus Sequences and series Graphs Graphs Definition of slope Positive or negative slope Determine the slope of a line Equation of a line (slope-intercept form) Equation of a line (point slope form) Equation of a line from graph Domain and range Quadratic function Limits (approaches a constant) Limits (approaches infinity) Asymptotes Continuity and discontinuities Parallel, coincident and intersepting lines Introduction to Functions Limits Continuity Asymptotes Trigonometry Trigonometric ratios The reciprocal trigonometric ratios Trigonometric ratios of related angles Trigonometric identities Solving right angles Law of sines Law of cosines Domain of trigonometric functions Statistics Mean Median Mode Quartiles Deciles Percentiles Mean deviation Variance Standard Deviation Coefficient of variation Skewness kurtosis Frequency distribution Graphing statistics & Data Factorial Variations without repetition Variations with repetition Permutations without repetition Permutation with repetition Circular permutation Binomial coefficient Combinations without repetition Combinations with repetition
 Proportions Proportion An equation in which two ratios are equal is called a proportion. Two ratios and are a proportion when Remember the two ratios are equals if their cross products are equal a·d = b·c You can also use the cross product to find a missing number: Solve: $\frac{-5}{2}=\frac{t}{-8}$$\fs2(-5)(-8)=2t\;\Rightarrow\;\;40=2t\;\Rightarrow\;2t=40\;\Rightarrow\;\;t=20$ Find x to get a proportion $\frac{10}{12}=\frac{x}{6}$. Find x to get a proportion: $\frac{18}{21}=\frac{42}{x}$ Solution x=