Surface area of a 4 × 3 × 2 box
Here's a small cardboard box, four units long, three units wide, and two units tall. How much cardboard does it take to make?
We can cut along the edges and lay the box flat. The flat shape is called a net.
Here it is — six rectangles, one for each face of the box.
The top and bottom match. Each is four by three, so twelve square units. Two of them is twenty-four.
The front and back match too. Each is four by two, so eight square units. Two of them is sixteen.
The two side faces are each three by two, so six square units. Two of them is twelve.
Now we add the six face areas: twelve plus twelve plus eight plus eight plus six plus six.
The surface area is fifty-two square units. That's how much cardboard the box needs!
Now you try. Find the surface area of this net. What is the surface area?