Surface Area

The last section is over surface area.  This can be hard because we have to imagine a 3d object and turn it in our minds.  I am going to do my best to show you can example.

Below we have a rectangular prism with dimensions of 1 x 1 x 4.  The order does not matter because we can flip this prism to fit what we need.

First, we are going draw a net on centimeter grid paper.  We start by drawing the face we can see.

Then, we draw outside flaps, which are 1 x 1.

We finish by matching up the other dimensions.  In this case, the rest will be 4 x 1.  We match up the 2 dimensions from the bases (1 x 1) and match it to our 3rd dimension, 4.

Now that we have our net, we can count the boxes each part covers.  OR, we can use the way shown below.

If you set all your dimensions out, 1 1 and 4, you can label them l w and h for length, width and height.  Then you have to multiply each one by the other one.  We have 3 numbers, so we will have 3 number sentences.  The D stands for dimension, and the A stands for area of the face.  LF means lateral faces, and lateral faces are congruent.  Since a prism has 6 sides, we can multiply each number sentence by 2 to find the area of both lateral faces. 

Always do the L X W, then L x H, then W x H.  It doesn't matter when one you call which since we are multiplying.  Then multiply each area by 2.  As you can see in picture, the surface area of this net/prism, is 18 cm^2