Find the length and area of the circle if the diameter (d) = 7 dm.

A circle is a flat geometric figure whose points are equidistant from a given point, the center of the circle.
1) Determine the circumference through the diameter:
l = πD,
where l is the circumference, D is the diameter, π = 3.14159.
l = 3.14 × 7 = 21.98 dm.
2) Calculate the area of the circle. Let’s write the formula:
S = πR²,
where R is the radius of the circle.
Find the radius of the circle:
R = D / 2 = 3.5 dm.
S = 3.14 × 3.5² = 3.14 × 12.25 = 38.47 dm².
Answer: the circumference is 21.98 dm., And the area is 38.47 dm²