Question

The shaded area in the diagram below shows the cross section of a square pyramid intersected by a plane parallel to the base. The pyramids edges are all 20 cm long.
http://go.flvs.net/courses/1/flvs_57_3641_12676/ppg/respondus/pool_Geom_3641_0709_28/image0044e613130.jpg
What is the perimeter of the shaded area?
Answer

21 cm

39 cm

49 cm

52 cm

Answer 1

the side edges of the shaded region will be proportional to 20 depending on the height of the pyramid and how high the intersecting plane is.
sorry your picture isn't opening for me
\[\frac{x}{h} = \frac{20}{H}\]
where H is height of pyramid, h is length from top to plane

Answer 2

We know that the upper square pyramid (with the shaded base) is similar to the larger square pyramid. Therefore we know that the ratio of the slopes is equal to the ratio of the base sides. Let x = base side of shaded area, then \[\frac{x}{13}=\frac{20}{20}\]

Answer 3

Once you have x, the perimeter of a square is given by\[P=4x\]

Answer 4

ok cool and how do i find x again? sorry

Answer 5

Solve the equation\[\frac{x}{13}=\frac{20}{20}\]