Correct variable declaration and return percentage

Fixed variable redeclaration and updated function to return percentage.

Author: mrafeie

Sprint-3/1-key-errors/1.js

@@ -2,6 +2,8 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+// An error will occur because `decimalNumber` is declared twice
+// inside the function: once as a parameter and again using `const`.
 
 // Try playing computer with the example to work out what is going on
 
@@ -15,6 +17,16 @@ function convertToPercentage(decimalNumber) {
 console.log(decimalNumber);
 
 // =============> write your explanation here
+// The function already has a parameter called decimalNumber.
+// The line const decimalNumber = 0.5 tries to declare another variable with the same name in the same scope.
+// JavaScript does not allow this, so a SyntaxError occurs.
+// There is also another problem: decimalNumber only exists inside the function, so console.log(decimalNumber) outside the function would cause a ReferenceError.
 
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+  return percentage;
+}
+
+console.log(convertToPercentage(0.5));