Step 1: According to the given measurements construct an image.

          GIVEN: Two poles AD and CE of height 6 m, 11 m respectively.

                          Distance between the feet of two poles (DC) = 12 m

                  From the figure:  AD = BC = 6 m      

                                              AB = DC = 12 m   (Since, opposite sides of the rectangles are equal.)

                                      It seems to be right angle triangle ABE

Step 2: Find the height of the right angle triangle

                EXPLANATION:  BE = CE - BC = 11- 6 = 5 m  

Step 3: Use the Pythagoras formula to find the distance between the tops of the poles.

             FORMULA:   (hypotenuse)^2 = (side)^2 + (side)^2

             EXAMPLE: AE^2 = AB^2 + BE^2

                                 AE^2 = (12)^2 + (5)^2

                                 AE^2 = 144 + 25

                                   AE = \sqrt{169}

                                      AE = 13 m

                  ∴  AE = distance between the two tops of the poles = 13 m