Step-by-step explanation:
pizza = circle
the area of a circle is
pi×r²
r = radius (half of the diameter). in our case 20/2 = 10".
the circumference of a circle is
2×pi×r
again, r = radius.
in our case that gives us
a.
2×pi×r = 2×pi×10 = 20×pi = 62.83185307... "
b.
the area of the pizza is
pi×10² = 100×pi = 314.1592654... in²
c.
it is 1/8 of the whole area, of course.
314.1592654... / 8 = 39.26990817... in²
d.
it is 1/8 if the whole circumference, of course.
62.83185307... / 8 = 7.853981634... "
