Net of a square pyramid base 10, slant height 12

Step by step

The question

Question: draw the net of a square pyramid, base 10, slant height 12, 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: the square base, with a triangle on each side.

2 Area of each face

The square base: 10 × 10 is 100.

Each triangle: half × 10 × 12 is 60.

Careful!

Count every face in the net.

There are four triangles.

3 Add them all

We add all 5 faces: 340.

4 Check

Let's check another way.

Four triangles of half 10 times 12 are two whole 10 by 12 rectangles: 240.

Plus the base 100.

Together 340.

So the answer is right!

Let's look back.

First: unfold it.

Then: area of each face.

Then: add them all.

Last: check.