Great for teaching the relationship between /- and x/?, (e.g.: 3 1=4 on one side, 4-1=3 on the reverse). Set of 90 classroom-sized cards. Measure 6-1/2" x 3-1/4" (16cm x 8cm). Titles in this series: ADDITION/SUBTRACTION DOUBLE VALUE FLASH CARDS, MULTIPLICATION/DIVISION DOUBLE VALUE FLASH CARDS