The map with a gap
David D. Connell and Jim Thurman
Mathnet detectives Kate Monday and George Frankly use math skills like triangulation and scale to find a buried treasure in a ghost town.

by Tom McCaughren (2011)
Four young boys find adventure involving ghosts and buried treasure when they set out to discover the secret behind the old legend of the golden key.
David D. Connell and Jim Thurman
Mathnet detectives Kate Monday and George Frankly use math skills like triangulation and scale to find a buried treasure in a ghost town.
Stephen Mooser
Horace and Mildred Flopbottom hire the young professionals of the Treasure Hounds organization to find out where Aunt Henrietta stashed her fortune before she died. Also includes two descriptions of actual treasures which have never been found.
Donald J. Sobol
Leroy Brown is back in the next six books in the Encyclopedia Brown series. As Idavilles ten-year-old star detective, Encyclopedia has an uncanny knack for trivia. With his unconventional knowledge, he solves mysteries for the neighborhood kids through his own detective agency. But his dad also happens to be the chief of the Idaville police department, and every night around the dinner table, Encyclopedia helps him solve some of the most baffling crimes. With ten confounding mysteries in each book, not only does Encyclopedia have a chance to solve them, but readers are given all the clues as well and can chime in with their own solutions. Interactive and funits classic Encyclopedia Brown!
Ron Roy
When doctored photographs of the President of the United States appear after an innocent Halloween party, his stepdaughter KC and her friend Marshall have to find the culprit in order to save the President's chances for re-election.