Question

I would like to know the formula that was used to get 120 cm

Answer 1

The given figure is a 2d representation of a 3d figure. If we wrap this figure, we get a building block.

In the figure below, the unknown edges are written:

Now, we have to find the area of all the polygons given in the figure. It consists of two same triangles and three different rectangles.

The area of the two triangles is given below:

`\begin{gathered} A=2*(1)/(2)*\text{base}*\text{height} \\ =\text{base}*\text{height} \\ =3*4 \\ =12 \end{gathered}`

Thus, the area of two triangles is 12 cm^2.

We know that the area of a rectangle is length times width. Now, the area of three rectangles is given below:

`\begin{gathered} A=9*5+9*4+9*3 \\ =45+36+27 \\ =108 \end{gathered}`

Thus, the area of three rectangles is 108 cm^2.

So, the total area is 12 + 108 = 120 cm^2.