High School Challenge




3 Unit Circles




Three unit circles are mutually tangent. There is a circle inscribed in the central region created by the three larger circles. This little circle is tangent to the other three. What is the radius of this little inscribed circle?


Correct Solutions:


  1. Assaf Romm. Brener HS, Israel
  2. Xingji Zheng. Abby Senior SH, Abbotsford, BC, Canada
  3. Maria Silvia Parra. Asunci6n de la Virgen, Buenos Aires, Argentina
  4. Ben Campbell. Nepean HS, Ottawa, Ontario, Canada
  5. Ken Scheiwe. New Trier HS, Winnetka, IL
  6. Matt Hartman. Granite Hills HS, El Cajon, CA
  7. Andy Hamada. Niles West HS, Skokie, IL
  8. Ming De Lin. Fair Lawn HS, NJ
  9. Sorin Ionescu. Ecole Secondaire Dorval, Dorval, Quebec, Canada
  10. Tammie Nimmo. Sauk Centre HS, Sauk Centre, MN
  11. Aaron Wills. Sauk Centre HS, Sauk Centre, MN
  12. Shannon Brunko. Sauk Centre HS, Sauk Centre, MN
  13. Vaul D Kranak. Century HS, Hillsboro, OR
  14. R. Perera. Sir Wilfrid Laurier Inst. Scarborough, Ontario, Canada
  15. Kolade Apata. Benjamin E. Mays HS, Atlanta, GA
  16. Laura Jensen. Arlington HS, Arlington, SD
  17. Joel Odland. Arlington HS, Arlington, SD
  18. Ross Campbell. Nepean HS, Ottawa, Ontario, Canada
  19. Loc Thai. Rostrevor College, Adelaide, South Australia
  20. Amy Inman. Century HS, Hillsboro, OR
  21. Mary Jane Cuyler. Century HS, Hillsboro, OR
  22. Ben Van Winkle. Century HS, Hillsboro, OR
  23. Leslie Gale. Century HS, Hillsboro, OR
  24. Aurelien Ramseyer. Kent-Meridian HS, Kent, WA
  25. Melvin Lee. Long Beach Polytech HS, Long Beach, CA
  26. Wojciech Lewkowicz. Lemont HS, Lemont, IL
  27. Scott Wessels. Granite Hills HS, El Cajon, CA
  28. Michelle Krysiak. Century HS, Hillsboro, OR
  29. Beth Wilson. Apollo JHS, Richardson, TX
  30. Philip Campbell. Agincourt PS, Ottawa, Ontario, Canada
  31. Casey Steffensen. Arlington HS, Arlington, SD
  32. Ranen Ghosh. Spruce Creek HS, Port Orange, FL
  33. Alex Wissner-Gross. Great Neck South HS, Great Neck, NY
  34. Douglas Baker. Hoffman Estates HS, Hoffman Estates, IL
  35. Enoch So. Ng Siu Mui Technical School, Kwai Chung, Hong Kong
  36. Slade Hart. Louisa County HS, Mineral, VA
  37. Steve Tomasello. Louisa County HS, Mineral, VA
  38. Jamel Jackson. Louisa County HS, Mineral, VA
  39. Elizabeth Harper. Louisa County HS, Mineral, VA
  40. Anthony Holland. Louisa County HS, Mineral, VA
  41. Travis Wood. Louisa County HS, Mineral, VA
  42. Terry Hoffman. Louisa County HS, Mineral, VA
  43. Mu'ad Dawod. Jubilee School, Amman, Jordan
  44. Tok Chewprecha. Century HS, Hillsboro, OR
  45. Bruce Chou. Spruce Creek HS, Port Orange, FL
  46. Randal West. Spruce Creek HS, Port Orange, FL
  47. Lars Erik Wall. Thor Heyerdahl VGS, Larvik, Norway
  48. Daniel Keith Johnson. Century HS, Hillsboro, OR
  49. Thomas Frosell. Lyman HS, Altamonte Springs, FL
  50. Jerry Fine. Merritt Island HS, Merritt Island, FL
  51. Mike Franks. Merritt Island HS, Merritt Island, FL
  52. Travis Lombard. Merritt Island HS, Merritt Island, FL
  53. Mike McDonald. Merritt Island HS, Merritt Island, FL
  54. Amanda Robinson. Merritt Island HS, Merritt Island, FL
  55. Clint Salamone. Merritt Island HS, Merritt Island, FL
  56. Rick Allison. Lyman HS, Longwood, FL
  57. Robert Rauch. Lake Mary HS, Lake Mary, FL
  58. Irina Khmelnitskaya. Carteret HS, Carteret, NJ
  59. Noha Negm. Carteret HS, Carteret, NJ
  60. Mauran Sivananthan. Carteret HS, Carteret, NJ
  61. Kim Wolf. Carteret HS, Carteret, NJ
  62. Jacqueline Sin. Stuartholme School, Brisbane, Australia
  63. Krina Patel. Carteret HS, Carteret, NJ