Answer:
2 mm
Step-by-step explanation:
let the radius of the semi-circle be r
Then,
length of curved portion = 1/2 x circumference = (1/2) (2)(π)r = πr
length of straight portion = diameter of circle = 2r
Hence, we can write an expression for the perimeter
Perimeter = length of curved portion + length of straight portion
Perimeter = πr + 2r
Perimeter = (π + 2)r
since we are given the perimeter = 5.14, assuming that π=3.14, our equation becomes:
5.14 = (3.14 + 2)r
5.14 = 5.14 r
r = 5.14 / 5.14 = 1
Hence, diameter = 2r = 2(1) = 2 mm
