Answer:
a. 31.4 inches
b. 314 square inches
Explanation:
You want to know the circumference of a pillow with a radius of 5 inches, and the area if the radius doubles.
Circumference
The formula for the circumference of a circle is ...
C = 2πr
For a radius of 5 inches, the circumference is about ...
C ≈ 2(3.14)(5 in) = 31.4 in
Jasmine will need about 31.4 inches of fringe.
Area
The formula for the are of a circle is ...
A = πr²
If the 5-in radius is doubled, it becomes 10 in, and the area becomes ...
A = π(10 in)² = 100π in² ≈ 314 in²
The area of the top of the pillow would be about 314 square inches.