Knowledge Base for Math Competitions

Counting and Probability

• 27_Probability1
• 28_Permutation
• 34_PermutationRepetition
• 35_Combination1
• 36_Combination2Identity
• 44_HandShakeProblem
• 54_Complement_En
• 54_Complement_Kr  (in Korean)

Pythagorean Theorem

• 09_Pythagorean1_Triplets
• 41_45_45_90_Triangle
• 49_PythagoreanTheoremAsAreas

Pythagorean Theorem on Special Right Triangles

• 1 Introduction
• 2 Introduction 2
• 3 Summary
• 4 Little Trick
• 5 45 45 90 Triangle1
• 6 45 45 90TriangleChart
• 7 30 60 90Triangle1
• 9 30 60 90TriangleChart

Number Theory

• 01_Divide By 25
• 02_Arithmetic Series
• 03_LCM
• 04_Grouping 1
• 05_FractionInequality1_Relative
• 06_FractionInequality2_Absolute
• 07_Prime Number Property 1
• 12_Repeating Decimal To Fraction 1
• 13_Even Odd Number Property
• 14_Power Of 2 Fractions
• 15_Exponent Manipulation
• 26_Power Of 2
• 29_Power Of 10 Computation
• 30_Divisibility By 3 And 9
• 31_Divisibility By 2 And 5
• 32_Divisibility By 6
• 33_Average Of Equally SpacedNumbers
• 48_Powers Of Ten In Disguise
• 45_Modulus Function
• 19_Arithmetic Sequence
• Power of 2 Addition Property
• Power of 2 Addition Geometric Illustration
• Power of 2 Denominator Fraction Addition Properties

Geometry

• 10_Area Of Circle Sectors
• 11_Area Of Equilateral Triangle
• 17_Perimeter Area Problem
• 24_Equal Areas Triangle_En
• 24_Equal Areas Triangle_Kr  (in Korean)
• 24_Equal Areas_Triangle
• 25_Equal Areas_Rectangle
• 40_Picks Theorem
• 42_Line Of Symmetry
• 43_City Block Distance
• 46_Area OfSquare Diagonal
• 50_Medians Of Triangle
• 51_1st Dimension to 2nd Demension
• 55_Inscribed Semi Circle_En
• 55_Inscribed Semi Circle_Kr  (in Korean)
• 56_Inscribed Cube Sphere_Kr  (in Korean)
• 56_Inscribed Cube Sphere_en
• 57_Quadratic Root Properties_En
• 57_Quadratic Root Properties_Kr  (in Korean)
• 59_Triangle Area Ratio_En
• 59_Triangle Area Ratio_Kr  (in Korean)
• 60_Triangle Inscribed Circle_En
• 60_Triangle Inscribed Circle_Kr  (in Korean)

Others

• 08_DefinedOperator
• 08_DefinedOperator_kr (in Korean)
• 16_SquareOf11Through31
• 18_ParallelResistors
• 20_MeanMedianMode
• 21_PercentIncreaseDecrease
• 21_PercentIncreaseDecrease_kr  (in Korean)
• 22_AngleBetweenHandsOfClock
• 23_Symmetry_Reflection
• 47_TelescopingSeries
• 52_AverageOfAverage
• 53_SolutionProblems
• 58_TrinomialExpansion_En
• 58_TrinomialExpansion_Kr  (in Korean)

Work Problems

• 37_WorkIntro
• 38_WorkPainting
• 39_WorkPoolFilling