speedConvert method
The function speedConvert converts a double value to a string with two decimal places and appends "x" at the end.
Args: volume (double): The volume parameter is a double value representing the speed that needs to be converted.
Returns: a string representation of the input volume, rounded to 2 decimal places, followed by the letter 'x'.
Implementation
String speedConvert(double volume) {
String value = volume.toStringAsPrecision(2);
return '$value x';
}