District of Columbia Grade 3 Math

Work through the example

An imaginary display mat is a rectangle 6 units long and 4 units wide. Each small square in the model has sides of 1 unit. Find how many unit squares cover the mat without gaps or overlaps. Then find how much ribbon would follow its outside edge once, with no extra for joining the ends.

Connect the model and calculation

Each of the four rows contains six unit squares. Four groups of six make 24, so the area is 24 square units. The multiplication 6 × 4 = 24 counts the covering squares; it does not count pieces of ribbon. For the outside edge, add the four side lengths: 6 + 4 + 6 + 4 = 20 units. There are two long sides and two short sides. Area measures the covered surface, while perimeter measures the distance around its boundary.

Understand an incorrect answer

If a student calls 20 the area, ask them to count one row of squares and then the rows. If 24 is given as the ribbon length, trace each edge and record its length separately. Adding 6 + 4 reaches only halfway around the rectangle. A correct number with the wrong unit still describes the wrong measurement: square units fit the covering task, and units of length fit the edge task.

Transfer the idea to another example

Change the rectangle to 5 units by 5 units. Its perimeter is still 20 units, but its area is 25 square units. Draw its five rows and compare them with the original four rows of six. These two rectangles show that an equal perimeter need not give an equal area. Then try a 3-by-8 rectangle: its area is 24 square units, matching the original, while its perimeter is 22 units. Ask the student to choose a measurement for a new task before calculating: covering a board and framing its edge require different information.

Selected DC Grade 3 references

The OSSE standards directory links the Common Core mathematics standards. DC adopted Common Core in July 2010. Use the adopted document and the school’s instructional sequence for planning. These labels describe the activity’s focus; the publisher’s mathematics document supplies the full expectations and mathematical practices.

Sources checked October 5, 2026. This selected activity supports instruction; it does not cover the whole grade’s curriculum.

Connect the explanation with practice

Choose a related skill from the lesson, worksheet, and quiz directory. Use the worked example to decide what needs support, then read the selected resource’s directions before assigning it.

DC CAPE Next begins with the spring 2027 administration. OSSE lists mathematics assessments in Grades 3–8 and says the educational standards have not changed. Confirm current participation and preparation guidance with the school. Read the DC CAPE Next changes and 2026–27 assessment policy.

The linked practice and books are independently published. Some editions may predate DC CAPE Next; check their contents and directions alongside current OSSE guidance rather than assuming their timer, question count, tools, or scoring matches the new assessment.

Keep one example of the student’s explanation with the practice result. Choose a smaller model, another related task, or a new context according to the difficulty shown in the activity.