Question

Find the perimeter of semi-circular plate of radius 3.85 cm.

Answer 1

Given: Radius r = 3.85 cm

Step-wise calculation:

1. Perimeter of a semicircle including the diameter 

= πr + 2r

= (π + 2)r 

2. Substitute r = 3.85 cm: 

πr = 3.14159265 × 3.85

= 12.0951317163 cm 

3. Diameter = 2r 

= 2 × 3.85

= 7.70 cm 

4. Perimeter = 12.0951317163 + 7.70 

= 19.7951317163 cm

Perimeter = (π + 2) × 3.85 cm  

= 19.795 cm   ...(To two decimal places)

= 19.80 cm