3.MD.D.8 Solve real-world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters.
3.NBT.A.2 Fluently add and subtract within $1000$ using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.