Chalk can be used to absorb grease stains. It acts as an absorbent by drawing the grease out of the fabric. Other methods like kerosene or petrol may damage the fabric.
In the adjoining figure, $\triangle CAB$ is a right triangle, right angled at A and $AD \perp BC$. Prove that $\triangle ADB \sim \triangle CDA$. Further, if $BC = 10$ cm and $CD = 2$ cm, find the length of AD.