Answers
   
   1) a)  8
      b)  8x9 = 72
      c)  4x5x7 = 14O
      d)  2x9x5 = 9O
      e)  88
      
   2) 81 is a square number
       8 is a cube number
       
   3) 66
   
   4) ....9, 16, 25, 36, 49, 64, 81
      ....27, 64, 125, 216, 343, 512
      
   5) .     .     .     .
      .     .     .     .
     35² = 3O x 4O + 25   (1225)
     45² = 4O x 5O + 25   (2O25)
     55² = 5O x 6O + 25   (3O25)
     65² = 6O x 7O + 25   (4225)