The floor of a guest room with a length of 35 decimeters and a width of 28 decimeters should be paved with square floor tiles. It is necessary to choose square tiles with a side length of how many decimeters to be clean and economical.
一间长35分米宽28分米的客房地面要铺正方形地砖，需选边长为多少分米的方砖才能既整洁又节约．
<result>7</result>