diff --git a/chapter04.js b/chapter04.js
index 12f6ef0..9160b68 100644
--- a/chapter04.js
+++ b/chapter04.js
@@ -9,42 +9,106 @@
 
 // Problem 1: The sum of a range
 function range(start, end, step=1) {
-  // Your code here
+  var size;
+  if(start <= end){
+    size = (end-start)/step;
+  }else{
+    size = (start-end)/step;
+  }
+  if(size < 0){
+    size *= -1;
+  }
+  var a = [];
+  var num = start;
+  for(var i = 0; i <= size; i++){
+    a[i] = num;
+    if(isNaN(step)){
+      num++
+    }else{
+      num += step;
+    }
+  }
+  return a;
 }
 
 function sum(array) {
-  // Your code here
+  var sum = 0;
+  for(var i = 0; i < array.length; i++){
+    sum += array[i];
+  }
+  return sum;
 }
 
 // Problem 2: Reversing an Array
 function reverseArray(array) {
-  // Your code here
+  var a_rev = [];
+  var end = array.length-1;
+  for(var i = 0; i < array.length; i++){
+    a_rev[i] = array[end];
+    end--;
+  }
+  return a_rev;
 }
 
 function reverseArrayInPlace(array) {
-  // Your code here
+  var end = array.length-1;
+  for(var i = 0; i < array.length/2; i++){
+    var tmp = array[i];
+    array[i] = array[end];
+    array[end] = tmp;
+    end--;
+  }
+  return array;
 }
 
 // Problem 3: A List
 function arrayToList(array) {
-  // Your code here
+  var list = null;
+  for(var i = array.length-1; i >= 0; i--){
+    list = {
+      value: array[i],
+      rest: list
+    }
+  }
+  return list;
 }
 
 function listToArray(list) {
-  // Your code here
+  var a = [];
+  for(var i = 0; isNaN(list); i++){
+    a[i] = list.value;
+    list = list.rest;
+  }
+  return a;
 }
 
 function nth(list, position) {
-  // Your code here
+  if(position == 0){
+    return list.value;
+  }
+  return nth(list.rest, position-1);
 }
 
 function prepend(element, list) {
-  // Your code here
+  list = {
+    value: element,
+    rest: list
+  }
+  return list;
 }
 
 // Problem 4: Deep comparison
 function deepEqual(obj1, obj2) {
-  // Your code here
+  if(typeof(obj1) != "object" || typeof(obj2) != "object"){
+    return obj1 === obj2;
+  }else{
+    for(var prop1 in obj1){
+      for(var prop2 in obj2){
+        return deepEqual(obj1[prop1], obj2[prop2]);
+      }
+    }
+  }
+  return obj1 === obj2;
 }
 
 
diff --git a/chapter05.js b/chapter05.js
index d1372cb..6e1e8eb 100644
--- a/chapter05.js
+++ b/chapter05.js
@@ -19,14 +19,40 @@ ancestry.forEach(function(person) {
 
 
 // Problem 1: Flattening
+function concat(a, b){
+  var a_end = a.length;
+  for(var i = 0; i < b.length; i++){
+    a[a_end] = b[i];
+    a_end++;
+  }
+  return a;
+}
+
 function flatten(arrays) {
-  // Your code here
+  var b = arrays[0];
+  for(var i = 1; i < arrays.length; i++){
+    b = concat(b, arrays[i]);
+  }
+  return b;
 }
 
 // Problem 2: Mother-child age difference
 /* This must return the average age difference instead of printing it */
 function averageMomChildAgeDiff() {
-  // Your code here
+	var tot_age_diff = 0;
+	var sample_size = 0;
+	ancestry.forEach(function(child){
+	  for(var mom in byName){
+	  	if(child.mother === byName[mom].name){
+	      var mom_age = child.born - byName[mom].born;
+	      tot_age_diff += mom_age;
+	      sample_size++;
+	      break;
+	    }
+	  }
+	});
+	var avg_age_diff = tot_age_diff/sample_size;
+	return avg_age_diff;
 }
 
 // Problem 3: Historical life expectancy
@@ -34,7 +60,26 @@ function averageMomChildAgeDiff() {
     for the century as the value
  */
 function averageAgeByCentury() {
-  // Your code here
+	var centuries = {};
+	ancestry.forEach(function(person){
+	  var century = Math.ceil(person.died / 100);
+	  var found = false;
+	  for(var c in centuries){
+	    if(c == century){
+	      centuries[century].push(person.died-person.born);
+	      found = true;
+	      break;
+	    }
+	  }
+	  if(!found){
+	    centuries[century] = [];
+	    centuries[century].push(person.died-person.born);
+	  }
+	});
+	for(c in centuries){
+		centuries[c] = average(centuries[c]);
+	}
+	return centuries;
 }
 
 
diff --git a/chapter13.js b/chapter13.js
index ab99bc6..bce99ea 100644
--- a/chapter13.js
+++ b/chapter13.js
@@ -10,6 +10,29 @@
 // Problem 1: Build table
 function buildTable(data) {
   // Your code here
+  var table = document.createElement("table");
+    var headrow = document.createElement("tr");
+    
+    for(var k of Object.keys(data[0])){
+      var headcell = document.createElement("th");
+      var cell = document.createTextNode(k);
+      headcell.appendChild(cell);
+      headrow.appendChild(headcell);
+      table.appendChild(headrow);
+    }
+    
+    for(var mount of data){
+      var bodyrow = document.createElement("tr");
+      
+      for(var m of Object.values(mount)){
+        var bodycell = document.createElement("td");
+        var cell = document.createTextNode(m);
+        bodycell.appendChild(cell);
+        bodyrow.appendChild(bodycell);
+      }
+      table.appendChild(bodyrow);
+    }
+    return table;
 }