diff --git a/chapter04.js b/chapter04.js
index 12f6ef0..15c825e 100644
--- a/chapter04.js
+++ b/chapter04.js
@@ -9,42 +9,112 @@
 
 // Problem 1: The sum of a range
 function range(start, end, step=1) {
-  // Your code here
+  let result = [];
+  if (!step) {
+      step = 1;
+  }
+  if (step < 0) {
+    for (i = start; i >= end; i += step) {
+      result.push(i);
+    }
+  }
+  else {
+    for (i = start; i <= end; i += step) {
+      result.push(i);
+    }
+  }
+  return result;
 }
 
 function sum(array) {
-  // Your code here
+  let total = 0;
+  array.forEach( (x) => { total += x; });
+  return total;
 }
 
 // Problem 2: Reversing an Array
 function reverseArray(array) {
-  // Your code here
+  let result = [];
+  for (let i = array.length - 1; i >= 0; i--) {
+    result.push(array[i]);
+  }
+  return result;
 }
 
 function reverseArrayInPlace(array) {
-  // Your code here
+  let l = array.length - 1;
+  for (let i = 0; i < array.length / 2; i++) {
+    let temp = array[i];
+    array[i] = array[l - i];
+    array[l - i] = temp;
+  }
+  return array;
 }
 
 // Problem 3: A List
 function arrayToList(array) {
-  // Your code here
+  let result = null;
+  for (let i = array.length - 1; i >= 0; i--) {
+    result = prepend(array[i], result);
+  }
+  return result;
 }
 
 function listToArray(list) {
-  // Your code here
+  let result = [];
+  for (let cursor = list; cursor != null; cursor = cursor.rest) {
+    result.push(cursor.value);
+  }
+  return result;
 }
 
 function nth(list, position) {
-  // Your code here
+  if (position == 0) {
+    return list.value;
+  }
+  for (let cursor = list; cursor; cursor = cursor.rest) {
+    return nth(cursor.rest, position - 1);
+  }
 }
 
 function prepend(element, list) {
-  // Your code here
+  let result = {
+    value: element,
+    rest: list
+  };
+  return result;
 }
 
+// -=-=-=-=-= helper func
+function isValid(element) {
+  return typeof element == "object" && element != null;
+}
+// -=-=-=-=-=-
+
 // Problem 4: Deep comparison
 function deepEqual(obj1, obj2) {
-  // Your code here
+  if (obj1 === obj2) {
+    return true;
+  }
+  else if (isValid(obj1) && isValid(obj2)) {
+    for (let prop in obj1) {
+      if (!obj2.hasOwnProperty(prop)) {
+        return false;
+      }
+      if (!deepEqual(obj2[prop], obj1[prop])) {
+        return false;
+      }
+    }
+    for (let prop in obj2) {
+      if (!obj1.hasOwnProperty(prop)) {
+        return false;
+      }
+      if (!deepEqual(obj1[prop], obj2[prop])) {
+        return false;
+      }
+    }
+    return true;
+  }
 }
 
 
diff --git a/chapter05.js b/chapter05.js
index d1372cb..28b30e2 100644
--- a/chapter05.js
+++ b/chapter05.js
@@ -17,16 +17,24 @@ ancestry.forEach(function(person) {
   byName[person.name] = person;
 });
 
-
 // Problem 1: Flattening
 function flatten(arrays) {
-  // Your code here
+  return arrays.reduce( (a, b) => {return a.concat(b); }, []); 
 }
 
 // Problem 2: Mother-child age difference
 /* This must return the average age difference instead of printing it */
+
 function averageMomChildAgeDiff() {
-  // Your code here
+  let ageDifferences = [];
+  let filteredAncestry = ancestry.filter( (person) => {return byName[person.mother] != null ? true : false;} );
+  filteredAncestry.forEach( (person) => {
+    let birth = person.born;
+    let motherDOB = byName[person.mother].born;
+    let ageDiff = birth - motherDOB;
+    ageDifferences.push(ageDiff); 
+  });
+  return average(ageDifferences);
 }
 
 // Problem 3: Historical life expectancy
@@ -34,10 +42,24 @@ function averageMomChildAgeDiff() {
     for the century as the value
  */
 function averageAgeByCentury() {
-  // Your code here
+  averageAges = {};
+  ancestry.forEach((person) => {
+    let century = Math.ceil(person.died / 100);
+    let age = person.died - person.born;
+    if (!averageAges.hasOwnProperty(century)) {
+      averageAges[century] = [age];
+    } else {
+      averageAges[century].push(age);
+    }
+  });
+  Object.keys(averageAges).forEach( (century) => { averageAges[century] = average(averageAges[century]); } )
+  return averageAges;
 }
 
 
+
+
+
 // Do not modify below here.
 module.exports = { flatten, averageMomChildAgeDiff, averageAgeByCentury };
 
diff --git a/chapter13.js b/chapter13.js
index ab99bc6..0a3937b 100644
--- a/chapter13.js
+++ b/chapter13.js
@@ -9,9 +9,45 @@
 
 // Problem 1: Build table
 function buildTable(data) {
-  // Your code here
+  let table = document.createElement("table");
+  let headings = Object.keys(data[0]);
+  let headerRow = createRow(headings, true);
+  table.appendChild(headerRow);
+  data.forEach( (element) => {
+    let rowData = Object.keys(data[0]).map((key) => {
+      return element[key];
+    });
+    let row = createRow(rowData);
+    table.appendChild(row);
+  });
+  return table
 }
 
+function createRow(data, isHeader) {
+  let row = document.createElement("tr");
+  data.forEach((element) => {
+    let col = createCol(element, isHeader);
+    row.appendChild(col);
+  });
+  return row;
+};
+
+function createCol(data, isHeader) {
+  let col;
+  if (isHeader){
+    col = document.createElement("th");
+  }
+  else{ 
+    col = document.createElement("td");
+  }
+
+  let content = document.createTextNode(data);
+  col.appendChild(content);
+  if (typeof data == "number"){
+    col.style.textAlign = "right";
+  }
+  return col;
+}
 
 // Do not modify below here.
 module.exports = { buildTable };
diff --git a/package-lock.json b/package-lock.json
index 5459d67..f414ca3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2,7 +2,6 @@
   "name": "eloquentjs-problems",
   "version": "1.0.0",
   "lockfileVersion": 1,
-  "requires": true,
   "dependencies": {
     "abab": {
       "version": "1.0.3",