If a local variable is declared but not used, it is dead code and should be removed. Doing so will improve maintainability because developers will not wonder what the variable is used for.
public function numberOfMinutes(hours:int):int
{
var seconds:int = 0; // seconds is never used
return hours * 60;
}
public function numberOfMinutes(hours:int):int
{
return hours * 60;
}