diff --git a/Sprint-3/1-key-errors/0.js b/Sprint-3/1-key-errors/0.js
index 653d6f5a0..1327a4414 100644
--- a/Sprint-3/1-key-errors/0.js
+++ b/Sprint-3/1-key-errors/0.js
@@ -1,13 +1,22 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// the function has a parameter str, but then tries to make a new
+// variable also called str. so maybe cause error because str already exists
 
 // 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;
-}
+//function capitalise(str) {
+//  let str = `${str[0].toUpperCase()}${str.slice(1)}`;
+//  return str;
+//}
 
 // =============> write your explanation here
+// SyntaxError: Identifier 'str' has already been declared
+// Prediction was correct, str already exists
 // =============> write your new code here
+
+function capitalise(str) {
+  const capitaliseStr = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return capitaliseStr;
+}
diff --git a/Sprint-3/1-key-errors/1.js b/Sprint-3/1-key-errors/1.js
index f2d56151f..5a0da345d 100644
--- a/Sprint-3/1-key-errors/1.js
+++ b/Sprint-3/1-key-errors/1.js
@@ -2,19 +2,41 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+//decimalNumber already exists as a parameter, so const decimalNumber is making
+//a new variable with the same name. There is also a problem where decimalNumber is being
+//assigned 0.5, which won't cause errors, but means that no matter what is passed to the function
+//decimalNumber will always be 0.5
 
 // Try playing computer with the example to work out what is going on
 
-function convertToPercentage(decimalNumber) {
-  const decimalNumber = 0.5;
-  const percentage = `${decimalNumber * 100}%`;
+//function convertToPercentage(decimalNumber) {
+//  const percentage = `${decimalNumber * 100}%`;
 
-  return percentage;
-}
+//  return percentage;
+//}
 
-console.log(decimalNumber);
+//convertToPercentage(0.6)
+//console.log(decimalNumber);
 
 // =============> write your explanation here
+//SyntaxError: Identifier 'decimalNumber' has already been declared
+//prediction correct, decimalNumber already exists so causes error. Removing the line
+//shows another error
+//console.log(decimalNumber);
+//            ^
+//ReferenceError: decimalNumber is not defined
+//This is because of scope, decimalNumber is defined in the function, so it only has scope
+//in the function
 
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+
+  return percentage;
+}
+
+let decimalNumber = 0.6;
+console.log(decimalNumber);
+console.log(convertToPercentage(decimalNumber));
diff --git a/Sprint-3/1-key-errors/2.js b/Sprint-3/1-key-errors/2.js
index aad57f7cf..1438d2a51 100644
--- a/Sprint-3/1-key-errors/2.js
+++ b/Sprint-3/1-key-errors/2.js
@@ -1,20 +1,26 @@
-
 // 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
+// In the function, 3 hasn't been assigned to num, so num is NaN and should return NaN.
+//Also when defining a function, the parameter should have the variable name, not a value
+//to pass in, unless you want to default value such as num = 3, which assigns 3 to num if
+// no value is passed in
 
-function square(3) {
-    return num * num;
-}
+//function square(3) {
+//    return num * num;
+//}
 
 // =============> write the error message here
-
+//SyntaxError: Unexpected number
 // =============> explain this error message here
-
+//syntaxError means there is a mistake in the way the code is written, so javascript can't
+// interpret the code. in this case there is a number here when there shouldn't be.
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
 
-
+function square(num) {
+  return num * num;
+}
diff --git a/Sprint-3/2-mandatory-debug/0.js b/Sprint-3/2-mandatory-debug/0.js
index b27511b41..74e23e0a4 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...
 
 // =============> write your prediction here
+//The multiply function doesn't return anything, only prints to console so the function call will have value undefined.
+//So when line 12 is executed, first it will print "The result of multiplying 10 and 32 is undefined"
+//Then on a new line it prints 320
 
-function multiply(a, b) {
-  console.log(a * b);
-}
+//function multiply(a, b) {
+//  console.log(a * b);
+//}
 
-console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
+//console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
 // =============> write your explanation here
-
+//It first printed 320, then printed "The result of multiplying 10 and 32 is undefined" on the next line
+//I think this is because it goes through the line 12, executes the multiply function call first, then finishes the
+//console.log function call.
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+
+function multiply(a, b) {
+  return a * b;
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
diff --git a/Sprint-3/2-mandatory-debug/1.js b/Sprint-3/2-mandatory-debug/1.js
index 37cedfbcf..ef7b55841 100644
--- a/Sprint-3/2-mandatory-debug/1.js
+++ b/Sprint-3/2-mandatory-debug/1.js
@@ -1,13 +1,23 @@
 // Predict and explain first...
 //  =============> write your prediction here
+//when the return line is executed, the function exits. a + b is a separate line because it
+//is after the semicolon, so a + b is never reached and not returned. So line 11 will print
+//The The sum of 10 and 32 is 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)}`);
 
 // =============> write your explanation here
+//It did as predicted, for the reason I expected
 // 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..42f75b5f6 100644
--- a/Sprint-3/2-mandatory-debug/2.js
+++ b/Sprint-3/2-mandatory-debug/2.js
@@ -1,24 +1,41 @@
 // Predict and explain first...
-
 // Predict the output of the following code:
+//The last digit of 42 is 3
+//The last digit of 105 is 3
+//The last digit of 806 is 3
 // =============> Write your prediction here
+//num is defined outside of the function, so has scope in the function getLastDigit.
+//the function doesn't take any arguments and uses num, so will always return 3, no matter what
+//is passed to the function because it will use num, which is set to 103
 
-const num = 103;
+//const num = 103;
 
-function getLastDigit() {
-  return num.toString().slice(-1);
-}
+//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
+// As I predicted, for the reason above
 // Finally, correct the code to fix the problem
 // =============> write your new code here
 
+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)}`);
+
 // This program should tell the user the last digit of each number.
 // Explain why getLastDigit is not working properly - correct the problem
diff --git a/Sprint-3/3-mandatory-implement/1-bmi.js b/Sprint-3/3-mandatory-implement/1-bmi.js
index 58b1085f1..6b39f4d69 100644
--- a/Sprint-3/3-mandatory-implement/1-bmi.js
+++ b/Sprint-3/3-mandatory-implement/1-bmi.js
@@ -16,4 +16,5 @@
 
 function calculateBMI(weight, height) {
   // return the BMI of someone based off their weight and height
+  return (weight / height ** 2).toFixed(1);
 }
diff --git a/Sprint-3/3-mandatory-implement/2-cases.js b/Sprint-3/3-mandatory-implement/2-cases.js
index 5b0ef77ad..fe92c4694 100644
--- a/Sprint-3/3-mandatory-implement/2-cases.js
+++ b/Sprint-3/3-mandatory-implement/2-cases.js
@@ -14,3 +14,6 @@
 // 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(inputString) {
+  return inputString.toUpperCase().replaceAll(" ", "_");
+}
diff --git a/Sprint-3/3-mandatory-implement/3-to-pounds.js b/Sprint-3/3-mandatory-implement/3-to-pounds.js
index 10754da73..d6f1144bd 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}`);
+}
+
+toPounds("10p");
+toPounds("100p");
+toPounds("232134p");
+toPounds("238p");
+toPounds("5234p");
diff --git a/Sprint-3/4-mandatory-interpret/time-format.js b/Sprint-3/4-mandatory-interpret/time-format.js
index c0dd9c9a5..6fd34cd30 100644
--- a/Sprint-3/4-mandatory-interpret/time-format.js
+++ b/Sprint-3/4-mandatory-interpret/time-format.js
@@ -22,17 +22,27 @@ function formatTimeDisplay(seconds) {
 
 // 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
+// 1. Last time it is called is pad(remainingSeconds). remainingSeconds = seconds % 60
+// with seconds = 61 this expression evaluates to 1, so when 1 is passed to pad, num is
+// assigned 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
+// "01". Num is 1 which converted to the string "1" which is assigned to numString.
+// The while loop runs while numString length less than 2, and adds "0"
+// to the beginning string. So "1" becomes "01". the string length is now equal to two,
+// so the while loop exits and numString is returned with value "01"
diff --git a/Sprint-3/5-stretch-extend/format-time.js b/Sprint-3/5-stretch-extend/format-time.js
index 32a32e66b..5cf4f51e2 100644
--- a/Sprint-3/5-stretch-extend/format-time.js
+++ b/Sprint-3/5-stretch-extend/format-time.js
@@ -1,25 +1,305 @@
 // This is the latest solution to the problem from the prep.
 // Make sure to do the prep before you do the coursework
 // Your task is to write tests for as many different groups of input data or edge cases as you can, and fix any bugs you find.
+function pad(num) {
+  let stringNum = num.toString();
+  if (stringNum.length < 2) {
+    stringNum = "0" + stringNum;
+    return stringNum;
+  } else {
+    return stringNum;
+  }
+}
+function formatAs12HourClock(time = "") {
+  if (typeof time != "string") {
+    return "Not a valid format"; //check if time is a string
+  }
+
+  if (/\s/.test(time)) {
+    return "Not a valid time"; //check for whitespace in string
+  }
+
+  if (
+    (time.indexOf(":") === -1 && time.indexOf(".") === -1) ||
+    (time.indexOf(":") !== -1 && time.indexOf(".") !== -1)
+  ) {
+    return "Not a valid time"; // check if there is only either one : or .
+  }
+
+  if (time.indexOf(":") === -1) {
+    if (time.indexOf(".") !== time.lastIndexOf(".")) {
+      return "Not a valid time"; //check there is only one .
+    }
+  }
+  if (time.indexOf(".") === -1) {
+    if (time.indexOf(":") !== time.lastIndexOf(":")) {
+      return "Not a valid time"; //check if there is only one :
+    }
+  }
+
+  let colonPeriodIndex = 0;
+  if (time.indexOf(":") === -1) {
+    colonPeriodIndex = time.indexOf(".");
+  } else {
+    colonPeriodIndex = time.indexOf(":");
+  }
+
+  if (
+    time.slice(0, colonPeriodIndex) === "" ||
+    time.slice(colonPeriodIndex + 1) === ""
+  ) {
+    return "Not a valid time"; //check if there is a number before and after time separator
+  }
+  const hours = Number(time.slice(0, colonPeriodIndex));
+  const minutes = Number(time.slice(colonPeriodIndex + 1));
+  const stringMinutes = pad(minutes);
+  const stringHours = pad(hours);
 
-function formatAs12HourClock(time) {
-  const hours = Number(time.slice(0, 2));
+  if (
+    isNaN(hours) ||
+    isNaN(minutes) ||
+    hours >= 24 ||
+    hours < 0 ||
+    minutes >= 60 ||
+    minutes < 0 ||
+    hours % 1 != 0 ||
+    minutes % 1 != 0
+  ) {
+    return "Not a valid time";
+  } //check if numbers are valid
+  if (hours === 12) {
+    return `${stringHours}:${stringMinutes} pm`;
+  }
+  if (hours === 0) {
+    return `12:${stringMinutes} am`;
+  }
   if (hours > 12) {
-    return `${hours - 12}:00 pm`;
+    return `${pad(hours - 12)}:${stringMinutes} pm`;
   }
-  return `${time} am`;
+
+  return `${stringHours}:${stringMinutes} am`;
 }
 
 const currentOutput = formatAs12HourClock("08:00");
 const targetOutput = "08:00 am";
 console.assert(
   currentOutput === targetOutput,
-  `current output: ${currentOutput}, target output: ${targetOutput}`
+  `current output: ${currentOutput}, target output: ${targetOutput}`,
 );
 
 const currentOutput2 = formatAs12HourClock("23:00");
 const targetOutput2 = "11:00 pm";
 console.assert(
   currentOutput2 === targetOutput2,
-  `current output: ${currentOutput2}, target output: ${targetOutput2}`
+  `current output: ${currentOutput2}, target output: ${targetOutput2}`,
+);
+
+const currentOutput3 = formatAs12HourClock("23:46");
+const targetOutput3 = "11:46 pm";
+console.assert(
+  currentOutput3 === targetOutput3,
+  `current output: ${currentOutput3}, target output: ${targetOutput3}`,
+);
+
+const currentOutput4 = formatAs12HourClock("12:00");
+const targetOutput4 = "12:00 pm";
+console.assert(
+  currentOutput4 === targetOutput4,
+  `current output: ${currentOutput4}, target output: ${targetOutput4}`,
+);
+
+const currentOutput5 = formatAs12HourClock("00:00");
+const targetOutput5 = "12:00 am";
+console.assert(
+  currentOutput5 === targetOutput5,
+  `current output: ${currentOutput5}, target output: ${targetOutput5}`,
+);
+
+const currentOutput6 = formatAs12HourClock("24:00");
+const targetOutput6 = "Not a valid time";
+console.assert(
+  currentOutput6 === targetOutput6,
+  `current output: ${currentOutput6}, target output: ${targetOutput6}`,
+);
+
+const currentOutput7 = formatAs12HourClock("47:00");
+const targetOutput7 = "Not a valid time";
+console.assert(
+  currentOutput7 === targetOutput7,
+  `current output: ${currentOutput7}, target output: ${targetOutput7}`,
+);
+
+const currentOutput8 = formatAs12HourClock("15:75");
+const targetOutput8 = "Not a valid time";
+console.assert(
+  currentOutput8 === targetOutput8,
+  `current output: ${currentOutput8}, target output: ${targetOutput8}`,
+);
+
+const currentOutput9 = formatAs12HourClock("18:60");
+const targetOutput9 = "Not a valid time";
+console.assert(
+  currentOutput9 === targetOutput9,
+  `current output: ${currentOutput9}, target output: ${targetOutput9}`,
+);
+
+const currentOutput10 = formatAs12HourClock("23:59");
+const targetOutput10 = "11:59 pm";
+console.assert(
+  currentOutput10 === targetOutput10,
+  `current output: ${currentOutput10}, target output: ${targetOutput10}`,
+);
+
+const currentOutput11 = formatAs12HourClock("00:01");
+const targetOutput11 = "12:01 am";
+console.assert(
+  currentOutput11 === targetOutput11,
+  `current output: ${currentOutput11}, target output: ${targetOutput11}`,
+);
+
+const currentOutput12 = formatAs12HourClock("12:01");
+const targetOutput12 = "12:01 pm";
+console.assert(
+  currentOutput12 === targetOutput12,
+  `current output: ${currentOutput12}, target output: ${targetOutput12}`,
+);
+
+const currentOutput13 = formatAs12HourClock("13:00");
+const targetOutput13 = "01:00 pm";
+console.assert(
+  currentOutput13 === targetOutput13,
+  `current output: ${currentOutput13}, target output: ${targetOutput13}`,
+);
+
+const currentOutput14 = formatAs12HourClock("hello");
+const targetOutput14 = "Not a valid time";
+console.assert(
+  currentOutput14 === targetOutput14,
+  `current output: ${currentOutput14}, target output: ${targetOutput14}`,
+);
+
+const currentOutput15 = formatAs12HourClock("15:ab");
+const targetOutput15 = "Not a valid time";
+console.assert(
+  currentOutput15 === targetOutput15,
+  `current output: ${currentOutput15}, target output: ${targetOutput15}`,
+);
+
+const currentOutput16 = formatAs12HourClock("12");
+const targetOutput16 = "Not a valid time";
+console.assert(
+  currentOutput16 === targetOutput16,
+  `current output: ${currentOutput16}, target output: ${targetOutput16}`,
+);
+
+const currentOutput17 = formatAs12HourClock("12:30abc");
+const targetOutput17 = "Not a valid time";
+console.assert(
+  currentOutput17 === targetOutput17,
+  `current output: ${currentOutput17}, target output: ${targetOutput17}`,
+);
+
+const currentOutput18 = formatAs12HourClock("1.30");
+const targetOutput18 = "01:30 am";
+console.assert(
+  currentOutput18 === targetOutput18,
+  `current output: ${currentOutput18}, target output: ${targetOutput18}`,
+);
+
+const currentOutput19 = formatAs12HourClock("15.30");
+const targetOutput19 = "03:30 pm";
+console.assert(
+  currentOutput19 === targetOutput19,
+  `current output: ${currentOutput19}, target output: ${targetOutput19}`,
+);
+
+const currentOutput20 = formatAs12HourClock("01.30");
+const targetOutput20 = "01:30 am";
+console.assert(
+  currentOutput20 === targetOutput20,
+  `current output: ${currentOutput20}, target output: ${targetOutput20}`,
+);
+
+const currentOutput21 = formatAs12HourClock("12.30:45");
+const targetOutput21 = "Not a valid time";
+console.assert(
+  currentOutput21 === targetOutput21,
+  `current output: ${currentOutput21}, target output: ${targetOutput21}`,
+);
+
+const currentOutput22 = formatAs12HourClock("12::30");
+const targetOutput22 = "Not a valid time";
+console.assert(
+  currentOutput22 === targetOutput22,
+  `current output: ${currentOutput22}, target output: ${targetOutput22}`,
+);
+
+const currentOutput23 = formatAs12HourClock("12..30");
+const targetOutput23 = "Not a valid time";
+console.assert(
+  currentOutput23 === targetOutput23,
+  `current output: ${currentOutput23}, target output: ${targetOutput23}`,
+);
+
+const currentOutput24 = formatAs12HourClock("12:");
+const targetOutput24 = "Not a valid time";
+console.assert(
+  currentOutput24 === targetOutput24,
+  `current output: ${currentOutput24}, target output: ${targetOutput24}`,
+);
+
+const currentOutput25 = formatAs12HourClock("12.");
+const targetOutput25 = "Not a valid time";
+console.assert(
+  currentOutput25 === targetOutput25,
+  `current output: ${currentOutput25}, target output: ${targetOutput25}`,
+);
+
+const currentOutput26 = formatAs12HourClock(":30");
+const targetOutput26 = "Not a valid time";
+console.assert(
+  currentOutput26 === targetOutput26,
+  `current output: ${currentOutput26}, target output: ${targetOutput26}`,
+);
+
+const currentOutput27 = formatAs12HourClock(".");
+const targetOutput27 = "Not a valid time";
+console.assert(
+  currentOutput27 === targetOutput27,
+  `current output: ${currentOutput27}, target output: ${targetOutput27}`,
+);
+
+const currentOutput28 = formatAs12HourClock("15:-30");
+const targetOutput28 = "Not a valid time";
+console.assert(
+  currentOutput28 === targetOutput28,
+  `current output: ${currentOutput28}, target output: ${targetOutput28}`,
+);
+
+const currentOutput29 = formatAs12HourClock("-15:30");
+const targetOutput29 = "Not a valid time";
+console.assert(
+  currentOutput29 === targetOutput29,
+  `current output: ${currentOutput29}, target output: ${targetOutput29}`,
+);
+
+const currentOutput30 = formatAs12HourClock(" :30");
+const targetOutput30 = "Not a valid time";
+console.assert(
+  currentOutput30 === targetOutput30,
+  `current output: ${currentOutput30}, target output: ${targetOutput30}`,
+);
+
+const currentOutput31 = formatAs12HourClock("12:30  ");
+const targetOutput31 = "Not a valid time";
+console.assert(
+  currentOutput31 === targetOutput31,
+  `current output: ${currentOutput31}, target output: ${targetOutput31}`,
+);
+
+const currentOutput32 = formatAs12HourClock("12:30\n");
+const targetOutput32 = "Not a valid time";
+console.assert(
+  currentOutput32 === targetOutput32,
+  `current output: ${currentOutput32}, target output: ${targetOutput32}`,
 );