diff --git a/Sprint-3/1-key-errors/0.js b/Sprint-3/1-key-errors/0.js
index 653d6f5a0..7163d38b4 100644
--- a/Sprint-3/1-key-errors/0.js
+++ b/Sprint-3/1-key-errors/0.js
@@ -1,13 +1,21 @@
 // Predict and explain first...
-//  =============> write your prediction here
+// Prediction: I predict that the code will produce an error because
+// str is already declared as a function parameter and is declared
+// again with 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;
+  return `${str[0].toUpperCase()}${str.slice(1)}`;
 }
 
-// =============> write your explanation here
-// =============> write your new code here
+// Explanation: The parameter str is already declared when the
+// function is created. We cannot declare another variable called
+// str with let in the same scope.
+
+// New code:
+// The function now uses the existing str parameter and returns
+// the capitalised string.
+
+console.log(capitalise("hello"));
\ No newline at end of file
diff --git a/Sprint-3/1-key-errors/1.js b/Sprint-3/1-key-errors/1.js
index f2d56151f..3caa2e5c5 100644
--- a/Sprint-3/1-key-errors/1.js
+++ b/Sprint-3/1-key-errors/1.js
@@ -1,20 +1,28 @@
 // Predict and explain first...
 
 // Why will an error occur when this program runs?
-// =============> write your prediction here
+// Prediction: An error will occur because decimalNumber is already
+// declared as a function parameter and is declared again with const.
+// Also, decimalNumber is being used outside the function where it
+// is not available.
 
 // Try playing computer with the example to work out what is going on
 
 function convertToPercentage(decimalNumber) {
-  const decimalNumber = 0.5;
   const percentage = `${decimalNumber * 100}%`;
 
   return percentage;
 }
 
-console.log(decimalNumber);
+console.log(convertToPercentage(0.5));
 
-// =============> write your explanation here
+// Explanation: The function parameter decimalNumber already contains
+// the value we give to the function. We cannot declare another
+// decimalNumber inside the function with const. The original code
+// also tried to use decimalNumber outside the function, where it
+// does not exist.
 
 // Finally, correct the code to fix the problem
-// =============> write your new code here
+
+// New code: The function uses the decimalNumber parameter and returns
+// the percentage. We call the function with 0.5 and log the result.
\ No newline at end of file
diff --git a/Sprint-3/1-key-errors/2.js b/Sprint-3/1-key-errors/2.js
index aad57f7cf..af55816b8 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
 
+// Prediction: I predict that an error will occur because 3 cannot
+// be used as a function parameter name.
+
 // =============> write your prediction of the error here
 
-function square(3) {
+function square(num) {
+
     return num * num;
+
 }
 
 // =============> write the error message here
 
+// SyntaxError: Unexpected number
+
 // =============> explain this error message here
 
+// The error happens because 3 is a number, not a valid parameter name.
+// A function parameter needs to be a variable name, such as num.
+
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
 
-
+console.log(square(3));
\ No newline at end of file
diff --git a/Sprint-3/2-mandatory-debug/0.js b/Sprint-3/2-mandatory-debug/0.js
index b27511b41..b84374400 100644
--- a/Sprint-3/2-mandatory-debug/0.js
+++ b/Sprint-3/2-mandatory-debug/0.js
@@ -1,14 +1,25 @@
 // Predict and explain first...
 
+// Prediction: I predict that the function will print 320,
+// but the final message will say undefined because the function
+// does not return the result.
+
 // =============> write your prediction here
 
 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
 
+// Explanation: console.log() displays a value on the screen,
+// but return sends a value back from the function.
+// The original function used console.log() instead of return,
+// so the function returned undefined.
+
 // Finally, correct the code to fix the problem
-//  =============> write your new code here
+// =============> write your new code here
+
+// The corrected function returns the result of multiplying a and b.
\ No newline at end of file
diff --git a/Sprint-3/2-mandatory-debug/1.js b/Sprint-3/2-mandatory-debug/1.js
index 37cedfbcf..496acbb87 100644
--- a/Sprint-3/2-mandatory-debug/1.js
+++ b/Sprint-3/2-mandatory-debug/1.js
@@ -1,13 +1,21 @@
 // Predict and explain first...
+
+// Prediction: I predict that the function will return undefined
+// because return stops the function before a + b can be calculated.
+
 //  =============> write your prediction here
 
 function sum(a, b) {
-  return;
-  a + b;
+  return a + b;
 }
 
 console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
+// Explanation: The original code used return on its own line.
+// When JavaScript reaches return, the function stops and returns
+// undefined. The line a + b is therefore never used.
+// We need to return a + b together.
+
 // =============> write your explanation here
 // Finally, correct the code to fix the problem
-//  =============> write your new code here
+// =============> write your new code here
\ No newline at end of file
diff --git a/Sprint-3/2-mandatory-debug/2.js b/Sprint-3/2-mandatory-debug/2.js
index 57d3f5dc3..2bf7df029 100644
--- a/Sprint-3/2-mandatory-debug/2.js
+++ b/Sprint-3/2-mandatory-debug/2.js
@@ -1,12 +1,15 @@
 // Predict and explain first...
 
 // Predict the output of the following code:
+// Prediction: I predict that the program will print 3 for all
+// three numbers because the function always uses the value 103.
+
 // =============> Write your prediction here
 
 const num = 103;
 
-function getLastDigit() {
-  return num.toString().slice(-1);
+function getLastDigit(number) {
+  return number.toString().slice(-1);
 }
 
 console.log(`The last digit of 42 is ${getLastDigit(42)}`);
@@ -14,11 +17,25 @@ 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
+// Output after correction:
+// The last digit of 42 is 2
+// The last digit of 105 is 5
+// The last digit of 806 is 6
+
 // =============> write the output here
-// Explain why the output is the way it is
+
+// Explanation: The original getLastDigit function did not have
+// a parameter, so the numbers 42, 105, and 806 passed to the
+// function were ignored. Instead, the function always used the
+// global value 103, so it returned 3 every time.
+//
+// The corrected function has a parameter called number.
+// This allows it to receive the number passed into the function.
+
 // =============> write your explanation here
+
 // 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
+// The function now receives a number as an argument and returns
+// its last digit.
\ No newline at end of file
diff --git a/Sprint-3/3-mandatory-implement/1-bmi.js b/Sprint-3/3-mandatory-implement/1-bmi.js
index 58b1085f1..2a839efde 100644
--- a/Sprint-3/3-mandatory-implement/1-bmi.js
+++ b/Sprint-3/3-mandatory-implement/1-bmi.js
@@ -15,5 +15,9 @@
 // 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
+  const bmi = weight / (height * height);
+
+  return bmi.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..0074bff2f 100644
--- a/Sprint-3/3-mandatory-implement/2-cases.js
+++ b/Sprint-3/3-mandatory-implement/2-cases.js
@@ -14,3 +14,7 @@
 // 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(input) {
+  return input.replaceAll(" ", "_").toUpperCase();
+}
\ No newline at end of file
diff --git a/Sprint-3/3-mandatory-implement/3-to-pounds.js b/Sprint-3/3-mandatory-implement/3-to-pounds.js
index 10754da73..e49d63f1c 100644
--- a/Sprint-3/3-mandatory-implement/3-to-pounds.js
+++ b/Sprint-3/3-mandatory-implement/3-to-pounds.js
@@ -1,6 +1,7 @@
-// In Sprint-1, there is a program written in 3-mandatory-interpret/3-to-pounds.js
+function toPounds(kg) {
+  return kg * 2.20462;
+}
 
-// You will need to take this code and turn it into a reusable block of code.
-// 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
+console.log(toPounds(1));
+console.log(toPounds(5));
+console.log(toPounds(10));
\ No newline at end of file
diff --git a/Sprint-3/4-mandatory-interpret/time-format.js b/Sprint-3/4-mandatory-interpret/time-format.js
index c0dd9c9a5..7ad684bf8 100644
--- a/Sprint-3/4-mandatory-interpret/time-format.js
+++ b/Sprint-3/4-mandatory-interpret/time-format.js
@@ -1,38 +1,16 @@
-function pad(num) {
-  let numString = num.toString();
-  while (numString.length < 2) {
-    numString = "0" + numString;
-  }
-  return numString;
-}
-
-function formatTimeDisplay(seconds) {
-  const remainingSeconds = seconds % 60;
-  const totalMinutes = (seconds - remainingSeconds) / 60;
-  const remainingMinutes = totalMinutes % 60;
-  const totalHours = (totalMinutes - remainingMinutes) / 60;
-
-  return `${pad(totalHours)}:${pad(remainingMinutes)}:${pad(remainingSeconds)}`;
-}
-
-// 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
-
-// Questions
-
 // a) When formatTimeDisplay is called how many times will pad be called?
-// =============> write your answer here
+// =============> 3
 
 // 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
+// =============> 0
 
 // c) What is the return value of pad when it is called for the first time?
-// =============> write your answer here
+// =============> "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
+// d) What is the value assigned to num when pad is called for the last time in this program? Explain your answer
+// =============> 1, because the remaining seconds are 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
+// e) What is the return value of pad when it is called for the last time in this program? Explain your answer
+// =============> "01", because pad adds a 0 to the front of 1.
\ No newline at end of file