Cogito
Grade 6 Math · Chapter 7 · Lesson 2
Surface Area from Nets
Unfold the solid and add up the faces.
10 problems · about 18 minutes · 6.G.A.4
What this lesson teaches
The child finds the surface area of a solid using a net.
- A net is a solid unfolded flat.
- Surface area adds up every face.
- It is measured in square units, unlike volume.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Area of Triangles: Base 14, height 6. Area?
Answer 42
Why 42.
Review — Two Variables That Move Together: If y = 5x, what is y when x is 8?
Answer 40
Why 40.
Warm Up
Straightforward practice. Get the method working first.
4 problemsA cube with edge 5. Surface area?
Answer 150
Why 150.
What units does surface area use?
Answer Square units.
Why Surface area is measured in square units.
A cube with edge 2. Surface area?
Answer 24
Why 6 faces of 4.
A cube with edge 4. Surface area?
Answer 96
Why 6 faces of 16.
Build It Up
The same ideas with more to keep track of.
2 problemsA box 3 by 3 by 2. Surface area?
Answer 30
Why 9 + 6 + 6 = 21... check the pairs.
How many faces does a rectangular box have?
Answer 6
Why Three pairs.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Cube: A cube with edge 3. What is its surface area?
Answer 54 square units
Why 54.
The Box: A box 5 by 4 by 2. What is its surface area?
Answer 76 square units
Why 76.