3rd Grade Area with Length and Width Worksheet

Before the formula, draw the first rectangle on grid paper with your child: 6 squares along and 3 rows down. Count the squares together, and you get 18. Then show that 3 rows of 6 is the same as 6 × 3, so the multiplication counts the squares faster. In the same way, the square of 4 mm by 4 mm holds 4 rows of 4, which makes 16.

Once this picture is clear, length × width stops being a rule to learn by heart.

Next, look at the unit in each answer. We measure a side in centimeters, but we measure an area in square centimeters, written cm². So the answers are 18 cm², 16 mm², 56 in² and 17 m². The original key wrote 16 square milliliters, which is a unit of volume. We corrected it to square millimeters before sharing the page.

Millimeters come back in 4th grade, so you can simply say that a millimeter is a very small step on a ruler.

To begin, compare the four answers with the answer key on page two. Then measure a book cover or a placemat with a ruler, in centimeters or in inches. Ask your child to multiply the two sides and to say the unit out loud. Finally, cover a small box lid with sticky notes, because counting them checks the multiplication.