A semicircle has a radius of 10. What is the approximate perimeter of the semicircle? Choose the most appropriate option:
A) 27
B) 33
C) 39
D) 45
E) 51

Rationale: "the perimeter of a circle is 2 * pi * r . the perimeter of a semicircle is 2 * pi * r / 2 + 2 r = pi * r + 2 r the perimeter is pi * 10 + 2 * 10 which is about 51 . the answer is e ."
Answer: E