There are $$21$$ trees planted along the road divider with trees planted at opposite ends. The trees are planted at regular intervals of $$2\text{m}$$. If some lamp posts are to be placed along the opposite side of the road at regular intervals of $$10\text{m}$$, how many lamp posts are required on the opposite side of the road if lamp posts are placed at opposite ends of the road? 
Overseas Competition->Knowledge Point->Word Problem Modules->Interval Problems->Straight Line Type with Objects on Both Sides