Look at the example in your workbook on page 328. Notice in the table that they have recorded the circumference and diameter for a small bowl. Let's look together at the circumference of a circle with the diameter of 5.
Make a circle with a diameter of 5.25 cm. Use the "unroll bar" and move the circle along the ruler to measure the circumference. Write the measured cm below.
Make a circle with a diameter of 7.8 cm. Use the "unroll bar" and move the circle along the ruler to measure the circumference. Write the measured cm below.
Make a circle with a diameter of 10.5 cm. Use the "unroll bar" and move the circle along the ruler to measure the circumference. Write the measured cm below.