Respuesta :

Let the unknown height be the x. This height is the product of the height of each stack (S) to the number of stacks (n) present. 
                                          x = Sn
Substituting the known values, 
                                   x = (6 5/8 in)(4) = 26 1/2 in
Thus, the height of 4 stacks is 26.5 inches.