Two poles of lengths 10 ft and 15 ft are set up vertically with their bases on horizontal ground 12 ft apart. Find the distance between the tops of the poles.

When we connect the ends of the poles and the project the horizontal line from the end of the 10-ft pole to the other pole, we form a right triangle with the legs equal to 12 ft and difference of the lengths of the pole. Using the Pythagorean theorem,

h² = sqrt ((12 ft) ² + (15 - 10) ²)

h = 13 ft

Thus, the distance between the tops of the poles is equal to 13 ft.