diff --git a/Sprint-3/1-key-errors/0.js b/Sprint-3/1-key-errors/0.js
index 653d6f5a0..6200eeb23 100644
--- a/Sprint-3/1-key-errors/0.js
+++ b/Sprint-3/1-key-errors/0.js
@@ -1,13 +1,15 @@
 // Predict and explain first...
-//  =============> write your prediction here
-
+//  =============> write your prediction here==> SyntaxError because str is declared twice (parameter + let)
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
-
+//function capitalise(str) {
+// let str = `${str[0].toUpperCase()}${str.slice(1)}`;
+// return str;
+//}
+// =============> write your explanation here==> (let str) will make a syntaxerror because str is already declared as parameter in the function: [function capitalise(str) ] and we can not declare an identifier in the same scope
+// =============> write your new code here:
 function capitalise(str) {
-  let str = `${str[0].toUpperCase()}${str.slice(1)}`;
-  return str;
+ str = `${str[0].toUpperCase()}${str.slice(1)}`;
+ return str;
 }
-
-// =============> write your explanation here
-// =============> write your new code here
+console.log(capitalise("hello world"));
diff --git a/Sprint-3/1-key-errors/1.js b/Sprint-3/1-key-errors/1.js
index f2d56151f..36bef60fd 100644
--- a/Sprint-3/1-key-errors/1.js
+++ b/Sprint-3/1-key-errors/1.js
@@ -1,20 +1,17 @@
 // Predict and explain first...
-
 // Why will an error occur when this program runs?
-// =============> write your prediction here
+// Prediction: SyntaxError — decimalNumber is a parameter and is redeclared with const inside the function.
+// Also, console.log(decimalNumber) outside the function would cause ReferenceError (not in that scope).
 
-// Try playing computer with the example to work out what is going on
+// Explanation:
+// 1) You cannot declare const decimalNumber when decimalNumber is already a parameter in the same scope.
+// 2) decimalNumber only exists inside the function, so logging it outside fails.
+// Fix: use the parameter (do not reassign it) and call the function in console.log.
 
 function convertToPercentage(decimalNumber) {
-  const decimalNumber = 0.5;
   const percentage = `${decimalNumber * 100}%`;
-
   return percentage;
 }
 
-console.log(decimalNumber);
-
-// =============> write your explanation here
+console.log(convertToPercentage(0.5));
 
-// Finally, correct the code to fix the problem
-// =============> write your new code here
diff --git a/Sprint-3/1-key-errors/2.js b/Sprint-3/1-key-errors/2.js
index aad57f7cf..8aa65d6ef 100644
--- a/Sprint-3/1-key-errors/2.js
+++ b/Sprint-3/1-key-errors/2.js
@@ -1,20 +1,29 @@
-
 // Predict and explain first BEFORE you run any code...
-
 // this function should square any number but instead we're going to get an error
-
 // =============> write your prediction of the error here
+// Prediction: SyntaxError — you cannot use a number literal (3) as a parameter name.
+// Parameter names must be valid identifiers (e.g. num), not values.
+// The value 3 should be passed when calling the function, not in the definition.
 
-function square(3) {
-    return num * num;
-}
+//function square(3) {
+//return num * num;
+//}
 
 // =============> write the error message here
+// SyntaxError: Unexpected number
+// (exact wording can vary slightly by Node version, e.g. "Missing formal parameter")
 
 // =============> explain this error message here
+// In a function definition, the parentheses list parameter names (placeholders).
+// 3 is a value (argument), not a name, so JavaScript rejects it while parsing the file.
+// Even if that were fixed, num is not defined in the original code — the parameter
+// and the name used inside the function must match.
 
 // Finally, correct the code to fix the problem
-
 // =============> write your new code here
+function square(num) {
+  return num * num;
+}
 
+console.log(square(3)); 
 
diff --git a/Sprint-3/2-mandatory-debug/0.js b/Sprint-3/2-mandatory-debug/0.js
index b27511b41..f5cbba421 100644
--- a/Sprint-3/2-mandatory-debug/0.js
+++ b/Sprint-3/2-mandatory-debug/0.js
@@ -1,14 +1,13 @@
 // Predict and explain first...
-
-// =============> write your prediction here
+// Prediction: multiply logs 320 but returns undefined, so the template
+// string prints: "The result of multiplying 10 and 32 is undefined"
 
 function multiply(a, b) {
-  console.log(a * b);
+  return a * b;
 }
 
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
-// =============> write your explanation here
-
-// Finally, correct the code to fix the problem
-//  =============> write your new code here
+// Explanation: console.log inside a function only prints; it does not return
+// a value. Without return, the function result is undefined. Using return
+// gives 320 so the template string shows the correct message.
diff --git a/Sprint-3/2-mandatory-debug/1.js b/Sprint-3/2-mandatory-debug/1.js
index 37cedfbcf..442f01cb2 100644
--- a/Sprint-3/2-mandatory-debug/1.js
+++ b/Sprint-3/2-mandatory-debug/1.js
@@ -1,13 +1,24 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// Prediction: return; exits immediately with undefined, so a + b never runs
+// and the message shows "undefined".
 
-function sum(a, b) {
-  return;
-  a + b;
-}
+//function sum(a, b) {
+//  return;
+//  a + b;
+// }
 
-console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+//console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
 // =============> write your explanation here
+// Explanation: A bare return; returns undefined. The expression must be on
+// the same return statement: return a + b;
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function sum(a, b) {
+  return a + b;
+}
+
+console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+
diff --git a/Sprint-3/2-mandatory-debug/2.js b/Sprint-3/2-mandatory-debug/2.js
index 57d3f5dc3..fe87377d3 100644
--- a/Sprint-3/2-mandatory-debug/2.js
+++ b/Sprint-3/2-mandatory-debug/2.js
@@ -1,24 +1,43 @@
 // Predict and explain first...
-
 // Predict the output of the following code:
 // =============> Write your prediction here
+// Prediction: All three lines print "3" because getLastDigit has no parameter
+// and always uses the outer const num = 103 (last digit 3). The arguments
+// 42, 105, and 806 are ignored.
 
-const num = 103;
 
-function getLastDigit() {
-  return num.toString().slice(-1);
-}
+//const num = 103;
+
+//function getLastDigit() {
+//  return num.toString().slice(-1);
+//}
+
+//console.log(`The last digit of 42 is ${getLastDigit(42)}`);
+//console.log(`The last digit of 105 is ${getLastDigit(105)}`);
+//console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
-console.log(`The last digit of 42 is ${getLastDigit(42)}`);
-console.log(`The last digit of 105 is ${getLastDigit(105)}`);
-console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
 // Now run the code and compare the output to your prediction
 // =============> write the output here
+// The last digit of 42 is 3
+// The last digit of 105 is 3
+// The last digit of 806 is 3
+
 // Explain why the output is the way it is
 // =============> write your explanation here
+// getLastDigit() does not declare a parameter, so the values passed in
+// (42, 105, 806) are not available inside the function. It reads the
+// global num (103) every time, so slice(-1) always returns "3".
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
-
 // This program should tell the user the last digit of each number.
 // Explain why getLastDigit is not working properly - correct the problem
+
+function getLastDigit(num) {
+  return num.toString().slice(-1);
+}
+
+console.log(`The last digit of 42 is ${getLastDigit(42)}`);
+console.log(`The last digit of 105 is ${getLastDigit(105)}`);
+console.log(`The last digit of 806 is ${getLastDigit(806)}`);
diff --git a/Sprint-3/3-mandatory-implement/1-bmi.js b/Sprint-3/3-mandatory-implement/1-bmi.js
index 58b1085f1..3c3d31645 100644
--- a/Sprint-3/3-mandatory-implement/1-bmi.js
+++ b/Sprint-3/3-mandatory-implement/1-bmi.js
@@ -15,5 +15,7 @@
 // It should return a string of their Body Mass Index to 1 decimal place
 
 function calculateBMI(weight, height) {
-  // return the BMI of someone based off their weight and height
+  return (weight/(height*height)).toFixed(1);
 }
+
+console.log(calculateBMI(70, 1.73));
diff --git a/Sprint-3/3-mandatory-implement/2-cases.js b/Sprint-3/3-mandatory-implement/2-cases.js
index 5b0ef77ad..89e4166de 100644
--- a/Sprint-3/3-mandatory-implement/2-cases.js
+++ b/Sprint-3/3-mandatory-implement/2-cases.js
@@ -14,3 +14,11 @@
 // You will need to come up with an appropriate name for the function
 // Use the MDN string documentation to help you find a solution
 // This might help https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toUpperCase
+
+function toUpperSnakeCase(string) {
+  return string.toUpperCase().replaceAll(" ", "_");
+}
+
+console.log(toUpperSnakeCase("hello there"));       
+console.log(toUpperSnakeCase("lord of the rings")); 
+console.log(toUpperSnakeCase("upper snake case"));  
diff --git a/Sprint-3/3-mandatory-implement/3-to-pounds.js b/Sprint-3/3-mandatory-implement/3-to-pounds.js
index 10754da73..572177862 100644
--- a/Sprint-3/3-mandatory-implement/3-to-pounds.js
+++ b/Sprint-3/3-mandatory-implement/3-to-pounds.js
@@ -4,3 +4,28 @@
 // You will need to declare a function called toPounds with an appropriately named parameter.
 
 // You should call this function a number of times to check it works for different inputs
+
+function toPounds(penceString) {
+  const penceStringWithoutTrailingP = penceString.substring(
+    0,
+    penceString.length - 1
+  );
+
+  const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+
+  const pounds = paddedPenceNumberString.substring(
+    0,
+    paddedPenceNumberString.length - 2
+  );
+
+  const pence = paddedPenceNumberString
+    .substring(paddedPenceNumberString.length - 2)
+    .padEnd(2, "0");
+
+  return `£${pounds}.${pence}`;
+}
+
+console.log(toPounds("399p"));  
+console.log(toPounds("50p"));   
+console.log(toPounds("1729p")); 
+console.log(toPounds("5p"));    
diff --git a/Sprint-3/4-mandatory-interpret/time-format.js b/Sprint-3/4-mandatory-interpret/time-format.js
index c0dd9c9a5..dddc5a631 100644
--- a/Sprint-3/4-mandatory-interpret/time-format.js
+++ b/Sprint-3/4-mandatory-interpret/time-format.js
@@ -14,7 +14,7 @@ function formatTimeDisplay(seconds) {
 
   return `${pad(totalHours)}:${pad(remainingMinutes)}:${pad(remainingSeconds)}`;
 }
-
+console.log(formatTimeDisplay(61));
 // You will need to play computer with this example - use the Python Visualiser https://pythontutor.com/visualize.html#mode=edit
 // to help you answer these questions
 
@@ -22,17 +22,22 @@ function formatTimeDisplay(seconds) {
 
 // a) When formatTimeDisplay is called how many times will pad be called?
 // =============> write your answer here
+//3 times.
 
 // Call formatTimeDisplay with an input of 61, now answer the following:
 
 // b) What is the value assigned to num when pad is called for the first time?
 // =============> write your answer here
+//Ther value is 0.
 
 // c) What is the return value of pad when it is called for the first time?
 // =============> write your answer here
+// The value is "00".
 
 // d) What is the value assigned to num when pad is called for the last time in this program?  Explain your answer
 // =============> write your answer here
+//The value is "1" — last call is pad(remainingSeconds), and for 61 seconds that is 1.
 
 // e) What is the return value of pad when it is called for the last time in this program?  Explain your answer
 // =============> write your answer here
+//The value is ""01" — pad turns 1 into a two-digit string.