Implementation
C

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Other implementations
import "fmt"
s := fmt.Sprintf("%.1f%%", 100.0*x)
import java.text.DecimalFormat;
String s = new DecimalFormat("0.0%").format(x);
$s = sprintf "%.1f", $x*100;
let s = format!("{:.1}%", 100.0 * x);
import std.string : format;
string percent = format("%.1f%%", x * 100.0);
SysUtils
s :=format('%.1f%%', [100.0*x]);  
var s = "${(x * 100).toStringAsFixed(1)}%";
s = "%.1f%" % 100.0 * x
s = Numeric.showFFloat (Just 1) (100*x) "%"
s = '{:.1%}'.format(x)
$s = number_format($x * 100.0, 1) . '%';
s = "#{Float.round(x * 100, 1)}%"
s = string.format("%.1f%%", x*100)