This medium worksheet pairs equation drilling with a sorting task to push fact family thinking past automatic recall. Part A runs nine fill-ins built around the 4-9-13 and 5-8-13 families, including 4 + 9 = 13, 13 - 9 = 4, and 5 + 8 = 13, then closes with 7 + 9 = 16. Two different families that share the sum 13 give children practice noticing that the parts are what define the family, not just the whole.

Part B matches 5 + 6, 18 - 9, 4 + 8, and 16 - 9 to 7, 9, 11, and 12, mixing teen subtraction with smaller addition so children cannot rely on a pattern. This kind of switching is where first graders build true fluency rather than memorized order.