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7th Grade Math / Lesson 6: Surface Area

What will we be learning in this lesson?

  • In this lesson you will look at how to find the surface areas of different objects.
Vocabulary words are found in this purple color throughout the lesson. Remember to put these in your notebook.


  • The surface area of an object is the amount of area on the surface of each side of the object. If an object has six sides, you must find the area of each of those sides and add them all together to get the surface area of the object. If the object has 5 sides, find the areas of each of those 5 sides and add them together.

  • Reminder on finding areas of different shapes.

    Squares/rectangles:   base * height

    Triangles:     ½ *base*height

    Circles:  p * radius 2


  • Use the dimensions of the object to find the surface area.
  • Take a close look at what shapes all of the sides are.
  • The front and back are triangles.
  • The other three sides are rectangles.


  • If we start with the triangles:   ½ * base * height
                                                    ½ * 6 * 4 =   ½ * 24 = 12 sq cm
    There are two triangles so we have two areas of 12 sq cm

  • Now the rectangle that is on the bottom. The dimensions are 6cm by 2 cm. The area of this rectangle is 6 * 2 = 12 sq cm

  • The rectangle on the side has dimensions 5 cm by 2 cm.
    The area of that one is 5 * 2 = 10 sq cm

  • The last rectangle is the one that is slanted. The dimensions of this one are 7 cm by 2 cm. The area is 7 * 2 = 14 sq cm


  • Now we just need to take all of the individual areas and add them together to get the total surface area of the object.

  • The surface area of this object is 60 sq cm

  • This is the amount of area on the surfaces of the object.

  • Can you find the volume of a cylinder?
  • Go back to the classroom to get to your homework and any other items you need to attend to.