jmc

Using the volume formula $lwh=V$, the volume of water in the aquarium is $100\times 40\times 37=148,000{\text{ cm}}^3$. When the rock is put in, the water and the rock will occupy a box-shaped region with volume $148,000+1000=149,000{\text{ cm}}^3$. The volume of the water and the rock is $100\times 40\times h$, where $h$ is the new height of the water. $\text{The new volume}=4000h=149,000{\text{ cm}}^3$, so the new height is $$h=\frac{149000}{4000}=37.25\text{ cm}.$$After adding the rock, the water rises $37.25-37=\boxed{0.25\text{ cm}}$.

$$OR$$Because the shape of the rock is irrelevant, we may assume that the rock is shaped like a rectangular box with base measuring $100\text{ cm}\times 40\text{ cm}$ and height $h$ cm. Using the volume formula, $100\times 40\times h=1000$, so $h=\frac{1000}{100\times 40}=0.25\text{ cm}$. When the rock is put into the aquarium, the water level will rise by $\boxed{0.25\text{ cm}}$.