B Apply

21. A triangular prism has base edges 4 cm, 5 cm, and 6 cm long. Its lateral area is 300   cm 2 . 300 , cm squared , . What is the height of the prism?
22. Writing Explain how a cylinder and a prism are alike and how they are different.

23. Pencils A hexagonal pencil is a regular hexagonal prism, as shown below. A base edge of the pencil has a length of 4 mm. The pencil (without eraser) has a height of 170 mm. What is the area of the surface of the pencil that gets painted?

    

24. Open-Ended Draw a net for a rectangular prism with a surface area of 220   cm 2 . 220 , cm squared , .

25. Consider a box with dimensions 3, 4, and 5.

    1. Find its surface area.
    2. Double each dimension and then find the new surface area.
    3. Find the ratio of the new surface area to the original surface area.
    4. Repeat parts (a)–(c) for a box with dimensions 6, 9, and 11.
    5. Make a Conjecture How does doubling the dimensions of a rectangular prism affect the surface area?

26. Think About a Plan A cylindrical bead has a square hole, as shown below. Find the area of the surface of the entire bead.

    

    • Can you visualize the bead as a combination of familiar figures?
    • How do you find the area of the surface of the inner part of the bead?
27. Estimation Estimate the surface area of a cube with edges 4.95 cm long.

28. Error Analysis Your class is drawing right triangular prisms. Your friend's paper is below. What is your friend's error?

    

29. Packaging A cylindrical can of cocoa has the dimensions shown below. What is the approximate surface area available for the label? Round to the nearest square inch.

    

30. Pest Control A flour moth trap has the shape of a triangular prism that is open on both ends. An environmentally safe chemical draws the moth inside the prism, which is lined with an adhesive. What is the area of the trap that is lined with the adhesive?

    

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