Find the area of the unshaded part of the figure

  unshaded area = 25(4 -π) in^2 ≈ 21.46 in^2

Each of the shaded circles has a diameter of (20 in)/4 = 5 in, which also is the width of the enclosing rectangle. Then each circle has a radius of 2.5 in, and an area of ...

  A = πr^2 = π(2.5 in)^2 = 6.25π in^2

The four circles together have an area of ...

  4A = 4·(6.25π in^2) = 25π in^2

The area of the rectangle is the product of its length and width:

  A = LW = (20 in)(5 in) = 100 in^2

Since the circles are shaded, the unshaded area is the difference between the rectangle area and the total area of the four circles:

  unshaded area = (100 in^2) - (25π in^2) = 25(4 -π) in^2 ≈ 21.46 in^2

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".

the forst and 3rd

step-by-step explanation: