Fill-It-In Outline Mathematics

Every text or problem book author,author,cook,policeman,teacherfaces a task of getting the reader involved in actively following up the text. Learning mathematics is necessarily an active pursuit of knowledge. Many a stratagem have been devised to achieve the goal of enticing the student into the right mood and attitude. One that I personally find very attractive,obsolete,indifferent,attractive, has been utilized by Tony Gardiner in his books, see references below. The gist of his outline solution approach is in supplying almost complete solutions to every problem with crucial pieces of information omitted now and then. The reader - a student - is made to follow and learn from the logic of the mentor and also pass local tests of his or her grasp by filling in the missing pieces.

The problem collection below is an attempt to master the outline solutions approach in the dynamic on-line setting.

Most of the samples below can be classified as Word Problems, i.e. problems presented in a verbal form, which, in order to be solved, should be translated into the mathematical language. Several tutorials for such a translation are provided elsewhere.

    Word Problems

  1. A Freeloader
  2. A Word Problem with Pens and Pencils
  3. Abdul and 10 Thieves
  4. Billy is twice as old as Sally
  5. Cars and motorcycles
  6. Child and Adult Ticket Count
  7. Coin counting word problem
  8. Constrained Intermarriages
  9. Crab's Weight
  10. Diluted Paint
  11. Five siblings
  12. Half an egg wonder
  13. How old is Al?
  14. How old is Karen?
  15. Lemons by Dozen
  16. Problem #24 from the Rhind Papyrus
  17. Sweet Purchase
  18. The ass and the mule
  19. The lucky find
  20. The Number of Judges and the Number of Votes
  21. Thirty Clerks
  22. When Son Will Catch Father?
  23. Train on Bridge
  24. Doubling Investment for a Fee And Getting Zero


  25. Elves and Gnomes
  26. Knights and Knaves #1
  27. Knights and Knaves #2
  28. Knights and Knaves #3
  29. Robbery #1
  30. Robbery #2
  31. Robbery #3
  32. Robbery #4
  33. Sons and Fathers
  34. Who Has the Beard?


  35. Food of a Lifetime
  36. Grandfather's Bill
  37. Insect flight record
  38. Is GLOBALHELLFRY a Prime?
  39. M. Jordan and K. Abdul-Jabbar
  40. "Math trick" with two dice
  41. Mathematicians and Musicians
  42. Planeload
  43. Practical Relativity
  44. Question That Changes with Time
  45. Two Consecutive Numbers with Small Sum


  46. Bicubal Domino
  47. Graph with Nodes of Even Degree
  48. Graph without 3-Cycles
  49. Pythagorean Triples via Fibonacci Numbers


  1. A Cryptarithm for Middle School
  2. A Typical Age Problem
  3. Advancing a Millenium Problem
  4. All Powers of x are Constant
  5. Composition of Functions, an Exercise
  6. Filling Pool with Fluids
  7. Four Weighings Suffice
  8. Getting Your Rightful Share Back
  9. Improving on an Escalator
  10. Inequality with Logarithms
  11. Rabbits Reproduce; Integers Don't
  12. Ratios and Sharing
  13. Train on Bridge


  14. Average Number of Runs
  15. Getting Ahead by Two Points
  16. Multiple of 3 out of the Box
  17. What is the Color of the Remaining Ball?

    Number Theory

  18. AB × BA = 3154.
  19. A Cryptarithm: A + HA = HEE
  20. Diophantine Equation I
  21. Primes as differences of squares
  22. Simple division by 7
  23. Smallest multiple of 9 with no odd digits
  24. Three digit twister
  25. When 3AA1 is divisible by 9?
  26. When 3AA1 is divisible by 11?


  27. Angle Bisector in Square
  28. Angle in Right Triangle
  29. Angle Subtended by a Diameter
  30. Base and Area of an Isosceles Triangle
  31. Circle in a Square Inscribed in a Circle
  32. Collinearity in Tangent Circles
  33. Concurrence on a Circle
  34. Construction of the Angle Bisector
  35. Construction of the Perpendicular Bisector
  36. Equiangular p-gons
  37. Existence of the Circumcenter
  38. Existence of the Circumcenter, Indirect Proof
  39. Longitude, Latitude and Distance to the Equator
  40. Pedoe's Theorem
  41. Problem 1 from the Ninth Nordic Mathematical Contest (1994)
  42. Running Lemming
  43. Square in a Circle Inscribed in a Square
  44. Square in a Right Triangle
  45. Three Congruent Rectangles
  46. Three Touching Circles
  47. Triangle Areas in a Parallelogram
  48. Triangle Areas in a Parallelogram II
  49. Two Altitudes, One Midpoint
  50. Two Equilateral Triangles
  51. Two Touching Circles
  52. Volume of Fibonacci Tetrahedron


  53. The Schwarz Lantern Explained
  54. Volume and Area of Torricelli's Trumpet


  1. T. Gardiner, More Mathematical Challenges, Cambridge University Press, 2003
  2. T. Gardiner, The Mathematical Olympiad Handbook, Oxford University Press, 1997.

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Copyright © 1996-2012 Alexander Bogomolny


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