Educational Insights Math Trekker Addition-Subtraction, Grades 1+ Take the learning on the go with this portable, interactive, math facts game! Math Trekker drills addition and subtraction facts 1 to 12, plus mixed practice. Self correcting games with positive reinforcement and the desire to "beat your time" motivate kids to keep practicing! Built in carabineer attaches easily to a backpack. Requires 3 replaceable AG 13/LR44 batteries (included).