Answer: 20cm
Step-by-step explanation:
First, add up the 3 sides you already know.
6+6+3 = 15.
Now you have to find the length of the semi circle which is half the circumference of a circle.
The equation for the circumference is 2πr.
The diameter of the circle is 3 meaning the radius is 1.5.
Plug this into the equation.
2 * π * 1.5 and you get approximately 9.42
Since it is only have a circle, you have to divide this by 2 to get half the circumference.
When you do this, you get 4.71
Add up 15 and 4.71 and you get 19.71 which rounds up to 20.