well, you have a base perimeter of 30. So, the base of each triangular lateral face is 30/4 = 7.5
Now you can see what the side edges of the pyramid are, and there are four of them.
let 'er rip...
The perimeter of the base of the regular quadrilateral pyramid is P = 30 cm. Find the sum of all edges of this pyramid, if the perimeter of a lateral face is 27.5 cm
2 answers
The perimeter of the base is 30, and each of the edges is 7.5. So you already have 4 of the edges down.
Now you need to find all the lateral edges. If the perimeter of a lateral edge is 27.5, one of the edges is a base edge, and a base edge is 7.5. So if you subtract 7.5 from 27.5 you are left with the other two edges on the lateral face. So two edges on the lateral face, equal 20
There are 4 base edges, and 4 lateral edges. The base edges equal 30, two out of four of the lateral edges equal 20, so 4 lateral edges equal 40. 40 plus 30 = 70, giving you your answer.
Now you need to find all the lateral edges. If the perimeter of a lateral edge is 27.5, one of the edges is a base edge, and a base edge is 7.5. So if you subtract 7.5 from 27.5 you are left with the other two edges on the lateral face. So two edges on the lateral face, equal 20
There are 4 base edges, and 4 lateral edges. The base edges equal 30, two out of four of the lateral edges equal 20, so 4 lateral edges equal 40. 40 plus 30 = 70, giving you your answer.