Ramu our intrepid traveler goes to Egypt and is dazzled by its sphinxes and pyramids. At one such pyramid in Giza, he reads the inscription, "This pyramid was originally 28 levels tall with 4 faces". The pyramids are constructed by cubical blocks of rocks such that, on any face, the number of rocks at each level is one less than the level below it. He counts the number of rocks on one of the faces to be 10.0. Can you help Ramu find out how many levels have been lost over the last 4000 years due to the ravages of time?

• (Assuming that the number of rocks counted on a face to be "100" instead of "10.0")
  
  The pyramid is constructed originally with the top most level with 1 cubical rock. Thus the level below it will have 2 rocks at each face. it follows as 1,2,3,.... till the bottom most level which will have 28 rocks on a face(as there were 28 levels).
  
  As now the upper levels are lost, we start from bottom most level which has 28 rocks.
  28+27+26+ 19 (incomplete 4th level) = 100 rocks on a face.
  Thus we can say that top 24 levels have been lost and 4th level(from bottom) is also incomplete.
• 6 years agoHelpfull: Yes(8) No(2)
• it is 26 levels have been lost and 27 th level is partially lost.
• 6 years agoHelpfull: Yes(2) No(2)
• Sorry n=4 after solving
  n/2(2a+(n-1)d)=10
  So levels lost 28-4=24 levels lost
• 6 years agoHelpfull: Yes(2) No(0)
• Let n levels are left. So by forming AP series we have
  n,(n-1),(n-2),(n-3).......
  Given no. Of rocks count to be 10
  So by AP series sum formula
  n/2(2a+(n-1)d)
  Here a=1 because top level must have only one rock, and d=1(given level rock differ by one) so solving this n=5
  These are the levels left so levels lost are 28-5=23 .
• 6 years agoHelpfull: Yes(1) No(0)