Look at the attached image (my handwriting is not the best).
Intersecting tangents are congruent. With this knowledge, we can find the unknown side lengths.
Add all the numbers in the image together.
16+16+8+8+9+9+6+6=78
78 cm is your answer.
Let's find the area of each shape that makes up the prism. Let's first start with the triangles.
There are two identical triangles on both ends of the prisms. They have a height of 12 and a base 18. Let's find the area of both of the triangles.
12×18=216
216 is the area of both triangles. Each triangle has an area of 108 though.
Let's find the area of the two rectangles.
There are two identical rectangles that are 30 m by 15 m. Let's find the area of both.
30×15=450×2=900
So, the area of both rectangles together is 900.
Let's find the area of the rectangle that acts as the base in the picture.
There's only one and it's 30 m by 18 m.
30×18=540
Let's add everything together.
540+900+216
1440+216
1656
So, the surface area is 1656 m².
