Net of a triangular prism sides 3, 4, 5, length 10

Step by step

The question

Question: draw the net of a triangular prism, sides 3, 4, 5, length 10, and find its surface area.

The surface area is the area of all the outside faces together.

A net shows every face flat.

1 Unfold it

Flat: three rectangles in a row, and a triangle at each end.

2 Area of each face

The two triangles: half × 3 × 4 is 6.

The 3 by 10 rectangle: 3 × 10 is 30.

The 4 by 10 rectangle: 4 × 10 is 40.

The 5 by 10 rectangle: 5 × 10 is 50.

Careful!

Count every face in the net.

There are two triangles, one at each end.

3 Add them all

We add all 5 faces: 132.

4 Check

Let's check another way.

The three rectangles make one long strip: 12 by 10, that is 120.

Plus the two triangles, 12.

Together 132.

So the answer is right!

Let's look back.

First: unfold it.

Then: area of each face.

Then: add them all.

Last: check.