A cube of side $5 \mathrm{cm}$ is cut into as many $1 \mathrm{cm}$ cubes as possible. What is the ratio of the surface area of the original cube to that of the sum of the surface areas of the smaller cubes?

Radius of a cylinder is $\mathrm{r}$ and the height is $\mathrm{h}$. Find the change in the volume if the height is doubled.

Radius of a cylinder is $\mathrm{r}$ and the height is $\mathrm{h}$. Find the change in the volume if the height is doubled, and the radius is halved.

Radius of a cylinder is $\mathrm{r}$ and the height is $\mathrm{h}$. Find the change in the volume if the height remains the same, and the radius is halved.