diff --git a/chapter04.js b/chapter04.js
index 12f6ef0..7d70838 100644
--- a/chapter04.js
+++ b/chapter04.js
@@ -9,42 +9,88 @@
 
 // Problem 1: The sum of a range
 function range(start, end, step=1) {
-  // Your code here
+  array = [];
+  if (start < end) {
+    for (let i = start; i <= end; i+=step) { 
+      array.push(i);
+    } 
+  }
+  if (start > end) {
+    for (let i = start; i >= end; i+=step) { 
+      array.push(i);
+    } 
+  }
+  return array;
 }
 
 function sum(array) {
-  // Your code here
+  num = 0;
+  for (let i = 0; i < array.length; i++) {
+    num += array[i];
+  }
+  return num;
 }
 
 // Problem 2: Reversing an Array
 function reverseArray(array) {
-  // Your code here
+  newArray = [];
+  for (let i = array.length-1; i >= 0; i--) {
+  	newArray.push(array[i]);
+  }
+  return newArray;
 }
 
 function reverseArrayInPlace(array) {
-  // Your code here
+  let len = array.length, temp = 0;
+  for (let i = 0; i < len/2; i++) {
+    temp = array[i];
+  	array[i] = array[(len-1)-i];
+    array[(len-1)-i] = temp;
+  }
+  arrayValue = array;
 }
 
 // Problem 3: A List
 function arrayToList(array) {
-  // Your code here
+  let list = null;
+  for (let j = array.length - 1; j >= 0; j--) {
+  	list = { value: array[j], rest: list, };
+  }
+  return list;
 }
 
 function listToArray(list) {
-  // Your code here
+  let array = [];
+  while(list) {
+    array.push(list.value);
+    list = list.rest;
+  }
+  return array;
 }
 
 function nth(list, position) {
-  // Your code here
+  let n = 0;
+  while (n < position && list) {
+    list = list.rest;
+    n++;
+  }
+  return list.value;
 }
 
 function prepend(element, list) {
-  // Your code here
+  const newList = {
+    value: element,
+    rest: list
+  };
+  return newList;
 }
 
 // Problem 4: Deep comparison
 function deepEqual(obj1, obj2) {
-  // Your code here
+  if (typeof obj1 !== typeof obj2) return false;
+  else if (obj1 == obj2) return true;
+  deepEqual(obj1.rest, obj2.rest);
+  return false;
 }
 
 
diff --git a/chapter05.js b/chapter05.js
index d1372cb..5896689 100644
--- a/chapter05.js
+++ b/chapter05.js
@@ -1,4 +1,4 @@
-/*
+x/*
  * Add your solutions to the chapter 5 problems from the eloquentjs book.
  *    - DO NOT rename the functions below.
  *    - You may add other functions if you need them.
@@ -20,13 +20,22 @@ ancestry.forEach(function(person) {
 
 // Problem 1: Flattening
 function flatten(arrays) {
-  // Your code here
+  console.log(arrays.reduce(function(flat, current) {
+    return flat.concat(current);
+  }, []));
 }
 
 // Problem 2: Mother-child age difference
 /* This must return the average age difference instead of printing it */
 function averageMomChildAgeDiff() {
-  // Your code here
+  // Only get values for mother
+  var array = ancestry.filter(function(person) {
+    return byName[person.mother] != null;
+  // Get the birth date of the current array value
+  // Subtract that value from the birthdate of the mother from byName
+  }).map(function(person) {
+    return person.born - byName[person.mother].born;
+  });
 }
 
 // Problem 3: Historical life expectancy
@@ -34,7 +43,27 @@ function averageMomChildAgeDiff() {
     for the century as the value
  */
 function averageAgeByCentury() {
-  // Your code here
+  var centuries = {};
+  // Map through values of an array 'a'
+  a.map(function (person) {
+
+    // Century of death
+    var century = Math.ceil(person.died / 100);
+    // Age when died
+    var age = person.died - person.born;
+    // Check if century value doesn't exist yet
+    if (!(century in centuries)) {
+      // Insert the century, make it an array of the age
+      centuries[century] = [age];
+    } else {
+      // Otherwise, add the current age
+      centuries[century].push(age);
+    }
+  });
+  
+  for (var key in centuries) {
+    console.log(key + ': ' + average(centuries[key]).toFixed(3));
+  }
 }
 
 
diff --git a/chapter05.test.js b/chapter05.test.js
index d65ea62..3f3af15 100644
--- a/chapter05.test.js
+++ b/chapter05.test.js
@@ -32,4 +32,4 @@ describe('Ch.5, Problem 3: Historical life expectancy', () => {
     expect(result[20]).toBeCloseTo(84.66, 1);
     expect(result[21]).toBeCloseTo(94);
   });
-});
+});
\ No newline at end of file