Answer:
6
Step-by-step explanation:
We know that the area of a circle is equal to 
 .
.
A semi-circle is a half-circle, meaning that it will have half of the area of a full circle. 
Therefore, a semi-circle's area is equivalent to  .
.
Set this equation equal to 18 .
.
Solve for r.
We then find that r = 6.
Now, we need to find the circumference. We know that the equation for the circumference of a circle is 2 r. Since we only need the perimeter of half of a circle, our circumference equation will equal
r. Since we only need the perimeter of half of a circle, our circumference equation will equal  r.
r.
Plug 6 in for r.
The perimeter of the garden is equal to 6 .
.
 
        
             
        
        
        
Answer:
profit will be maximized by making 20 doodles and 20 paintings = ($10 x 20) + ($20 x 20) = $600 
Step-by-step explanation:
we have to maximize the following equation:
$10P + $20D
where:
P = number of portraits
D = number of doodles
the constraints are:
P + D ≤ 40
P ≤ 30
D ≤ 20
we do not need to use solver or any other type of linear programming tool to solve this, since profit will be maximized by making 20 doodles and 20 paintings = ($10 x 20) + ($20 x 20) = $600 
 
        
             
        
        
        
C definitely c hope this helps