multiplying two decimal point numbers

[gaurav.shetti]

how do I multiply two decimal point numbers Ie:

<$x=500>
<$y=0.5>
<$z=($x * $y)>

above method returns 0.

[mark]

<$x=(convert( '500.0' , 'double' ))>
<$y=(convert( '0.5' , 'double' ))>
<$z=($x * $y)>