# GRE Math

 Percent Change (Amt change/ original amt) x 100 Exponent opperations **Need the same base**Multiplying exponents: add the exponents and keep the same baseDividing exponents: subtract the exponents and keep the same baseRaise a power to a power: multiply the exponentsNegative exponents: 1/exponent expressionFraction exponents: root of the expression **Do NOT add or subtract exponents or roots** Absolute Value Never negative Multiplying Binomials FOIL Factoring Squares Factoring Binomials a2 - b2 = (a-b)(a+b) a2 +2ab + b2 = (a+b)2 a2 -2ab + b2 = (a-b)2 Quadratic Equation ax2 + bx + c = 0 Finding the distance between two points Midpoint d= sqrt (x1-x2)2 + (y1- y2)2 M= (x1+x2)/2 , (y1+y2)/2 Slope Midpoint m=slope= rise/run(y1-y2) = m(x1-x2) Circles and Angles (central and inscribed) central: angle = arc inscribed: angle = arc x2 Area of a triangle (1/2)base x height Adding fractions "magic x" (3/7) + (2/9) = 7 3x9 = 277x2 = 14 41 9x7 = 63 (41/63) = 7 Polygons (3+ sides) sum of interior angles: (n-2)180 sum of exterior angles: 360 Types of triangles Isosceles: 2 equal sides and anglesEquilateral: 3 equal side and anglesRight: 90 degree angle: a2 + b2 = c2 3-4-6: 6-8-10 30-60-90: x - sqrt3 - 2x 5-12-13 45-45-90: 1 - 1 - sqrt 2 Parallelograms A = base x height supplemental angels = 180 Circles Circumference: 2(pi)r Area: (pi)r2 Surface area -rectangular solid -cube rectangel: 2lw + 2wh + 2lh cube: 6s2 Volume -Rectangle -Cube -Cylinder Rectangle: lwhCube: l3Cylinder: (pi)r2h Trapezoid (one pair parallel sides, one pair non-parallel) a=(( s1 + s2)/2) xh Fractions: Decimals: Percentages to Know (1/2) : 0.5 : 50%(1/3) : 0.33 : 33.3%(1/4) : 0.25 : 25%(1/5) : 0.2 : 20%(2/3) : 0.66 : 66%(3/4): 0.75 : 75% Percent increase/decrease Percent increase: (amt of increase/original whole) x100Percent decrease: (amt of decrease/original whole) x100 How to recognize multiples 2: Last digit is even3: Sum of digits is a multiple of 34: Last two digits are a multiple of 45: Last digit is 5 or 06: Sum of digits is a multiple of 3 and last digit is even9: Sum of digits is multiple of 910: Last digit is 012: Sum of digits is a multiple of 3, and last two digits are a multiple of 4 Common Squared Numbers 1: 12: 43: 94: 165: 256: 367: 498: 649: 8110: 10011: 12112: 14413: 16914: 19615: 225 Common Square roots 225: 15196: 14169: 13144: 12121: 11 Authorlsleiter ID40214 Card SetGRE Math DescriptionFormulas Updated2010-10-06T17:36:17Z Show Answers