Lesson 12

What is Surface Area?

Let’s cover the surfaces of some three-dimensional objects.

Problem 1

What is the surface area of this rectangular prism?

2 by 4 by 4 unit rectangular prism 
A:

16 square units

B:

32 square units

C:

48 square units

D:

64 square units

Problem 2

Which description can represent the surface area of this trunk?

Photograph of a treasure chest
A:

The number of square inches that cover the top of the trunk.

B:

The number of square feet that cover all the outside faces of the trunk.

C:

The number of square inches of horizontal surface inside the trunk.

D:

The number of cubic feet that can be packed inside the trunk.

Problem 3

Which figure has a greater surface area?

Figure A 5 cubes arranged in L shape. Figure B 5 cubes arranged in a cross shape.

Problem 4

A rectangular prism is 4 units high, 2 units wide, and 6 units long. What is its surface area in square units? Explain or show your reasoning.

Problem 5

Draw an example of each of these triangles on the grid.

  1. A right triangle with an area of 6 square units.
  2. An acute triangle with an area of 6 square units.
  3. An obtuse triangle with an area of 6 square units.
Image of a grid.
(From Unit 1, Lesson 9.)

Problem 6

Find the area of triangle \(MOQ\) in square units. Show your reasoning.

Triangle MOQ enclosed in rectangle MNPR.

 

(From Unit 1, Lesson 10.)

Problem 7

Find the area of this shape. Show your reasoning.

A four-sided shape on a grid, with two sides that drop 5 units as they cross 5 units and meet at a right angle, and two sides that drop two units as they cross 5 units.
(From Unit 1, Lesson 3.)