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Subtract shapes

CONCEPTS

Tips

• Find the area of the shaded area by determining the volume or area of each shape separately. Then find the difference or the properties of the section being asked about


Circles can be broken down into quarters. Then subract the area of the quarter circles from the area of the square





Subtract the area of the smaller circle from the larger circle






The properties of a triangle can be determined by the properties of the square

PRACTICE PROBLEMS



Question 1 The square has side lengths = 8. Each vertex is the center of a circle. The circles are congruent and are tangent to each other. What is the area of the shaded region (see figure below)?


-- Answer -- 64 - 16 π

There are 4 quarter circles inside the square or 1 total circle. Area = πr² = π * 4² = 16 π

Area of square = 8 * 8 = 64

Area of shaded region = 64 - 16 π









Question 2 A box in a shape of a cube has interior side lengths of 18 inches. It is used to ship a right circular cylinder with a radius of 6 inches and a height of 12 inches. What is a mathematical expression that describes the area inside the cube that isn't filled by the right circular cylinder?


-- Answer -- 18³ - (π)(6²)(12)

volume of box = 18³

volume of right circular cylinder = π r² h = (π)(6²)(12)

Volume of area inside the cube that isn't filled by the right circular cylinder = 18³ - (π)(6²)(12)

ACT PRACTICE PROBLEMS

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