# 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? 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? 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? ### 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. (From Unit 1, Lesson 9.)

### Problem 6

Find the area of triangle $$MOQ$$ in square units. Show your reasoning. (From Unit 1, Lesson 10.)

### Problem 7

Find the area of this shape. Show your reasoning. (From Unit 1, Lesson 3.)