David Lubar 
Numbed! [PDF ebook] 

When Logan’s class takes a trip to a math museum, his mischievous friend Benedict is sure it will be a boring day-until he discovers a robot and its creator in an off-limits area. The robot proves feisty, and soon both boys get zapped. They realize only later that they’d left the museum without their math skills. To get back the knowledge they need for school-not to mention buying food at the mall, divvying up dinner at home, and much more-they’ll have to get back to the museum and pass a series of math challenges. Being "numbed" teaches Logan and Benedict just how useful, and even fun, math can be.