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 15 cm long.



What is the perimeter of the shaded area?

24 cm

36 cm

12 cm

42 cm

Answer 1

The section shadedcan be considered as base of the smaller pyramid with the side length as 6. Since the bigger pyramid and smaller pyramid are similar the ratio of sides must be same.
The ration lenght of side/bsae for bigger pyramid is (6+9)/15 = 1 same has to be the case for smaller pyramid

Which imlies the smaller pyramid has base of 6
Hence the perimeter is 6*4 = 24