1. The base of a cone is fixed to the top of a cylinder to make a decoration.

The radius of the base of the cone and of the cylinder is $r$ cm.
The cone’s height is 5$r$ cm.
The total height of the decoration is 6$r$ cm.
The total volume of the decoration is 225 cm³.

Calculate the value of $r$.
Show your working.

$r=$............................