A net unfolds a 3D shape into flat rectangles. To find surface area you find the area of each rectangle (length × width) and then add them all up. So this runs on area of a rectangle and adding several areas. Warm those up first.
Answer these 3, then press Show my path. No grade — this just points you to the right level.
1. Area of a rectangle that is 4 long and 3 wide?
2. Add the areas: 6 + 6 + 8?
3. Surface area is measured in which units?
A net shows every face of a box laid flat. The area of each rectangular face is length × width. To get surface area, find each face's area and add them all together. The answer is in square units.
Your quick check picks one for you, but you can switch any time:
Level 0 Find one rectangle's area, then add a couple.
A. Area of a 3 × 2 rectangle = ___
Area = length × width = 3 × 2 = 6.
B. Add two faces: 6 + 6 = ___
6 + 6 = 12.
C. Add a third face: 12 + 4 = ___
12 + 4 = 16.
Level 1 Find face areas, then add them.
A. Area of a 5 × 4 face = ___
5 × 4 = 20.
B. A net has faces of area 12, 12, and 8. Add them: ___
12 + 12 = 24, then 24 + 8 = 32.
C. How many faces (rectangles) does a box (rectangular prism) have?
A box has 6 faces: top, bottom, front, back, and two sides.
Level 2 Stretch: add a full set of face areas.
A. A net has faces of area 10, 10, 15, 15, 6, and 6. What is the total area?
10+10 = 20, +15+15 = 50, +6+6 = 62.
B. Two faces are 4 × 3 each. What is their combined area? (square units)
Each face is 4 × 3 = 12, and 12 + 12 = 24.
1. Area of a 6 × 3 rectangle?
6 × 3 = 18 square units.
2. Add the face areas: 8 + 8 + 5 + 5 = ___
8 + 8 = 16, then 5 + 5 = 10, and 16 + 10 = 26.
You've practiced exactly what Lesson 10-3 uses. Time to dive in.
Start Lesson 10-3 →