Let AB and CD are the two pole with height 6 m and 11 m respectively.
Therefore, CP = 11 – 6 = 5 m and AP = 12 m
In triangle APC, by pythagoras theorem
AP² + PC² = AC²
⇒ 12² = 5² = AC²
⇒ AC² = 144 + 25 = 169
⇒ AC = 13m
Hence, the distance between the tops of two poles is 13 m.