The fall festival fiasco

"Autumn has arrived and the fourth graders at Arthimos Elementary couldn't be more excited for the Fall Festival! But when the tickets go missing, the pie eating contest is sabotoged, and a suspiciously humongous pumpkin shows up, will anyone be able to save the day and catch the culprit? The school's best (and only) investigators are on the case, The Prime Detectives--Abby 'the Abacus' Feldstein, Cameron 'Cam' McGill, and Gabriel 'Gabe' Kim. Using arithmetic, geometry, and logic, the Prime Detectives will stop at nothing to figure out who did what, when, and why!"--Amazon.