7. 2100 cubes with a side length of 1 meter are stacked to form a solid rectangular prism. Its height is 10

meters, and both the length and width are greater than the height. What is the sum of the length and width of the rectangular prism in meters?
7.【Solution】Since the edge length of the cube is 1 meter, the volume of 2100 cubes stacked into a solid rectangular prism is 2100 cubic meters.
It is known that the height is 10 meters, so the length $\times$ width $=210$ square meters.
Factorize 210 into prime factors: $210=2 \times 3 \times 5 \times 7$
Since the length and width must be greater than the height (10 meters), the length and width can only be: $3 \times 5$ and $2 \times 7$. That is, 15 meters and 14 meters. 14 meters + 15 meters $=29$ meters.
Answer: The sum of the length and width is 29 meters.