diff --git a/chapter04.js b/chapter04.js
index 12f6ef0..89dd931 100644
--- a/chapter04.js
+++ b/chapter04.js
@@ -9,42 +9,86 @@
 
 // Problem 1: The sum of a range
 function range(start, end, step=1) {
-  // Your code here
+    if (step == null) step = 1;
+  var return_array = [];
+
+  if (step > 0) {
+    for (var i = start; i <= end; i += step)
+      return_array.push(i);
+  } else {
+    for (var i = start; i >= end; i += step)
+      return_array.push(i);
+  }
+  return return_array;
 }
 
 function sum(array) {
   // Your code here
+    var local_sum = 0;
+  for (var i = 0; i < array.length; i++)
+    local_sum += array[i];
+  return local_sum;
 }
 
 // Problem 2: Reversing an Array
 function reverseArray(array) {
   // Your code here
+    var return_var = [];
+  for (var i = array.length - 1; i >= 0; i--)
+    return_var.push(array[i]);
+  return return_var;
 }
 
 function reverseArrayInPlace(array) {
   // Your code here
+    for (var i = 0; i < Math.floor(array.length / 2); i++) {
+    var old = array[i];
+    array[i] = array[array.length - 1 - i];
+    array[array.length - 1 - i] = old;
+  }
+  return array;
 }
 
 // Problem 3: A List
 function arrayToList(array) {
   // Your code here
+    var my_list = null;
+  for (var i = array.length - 1; i >= 0; i--)
+    my_list = {value: array[i], rest: my_list};
+  return my_list;
 }
 
 function listToArray(list) {
   // Your code here
+    var array = [];
+  for (var node = list; node; node = node.rest)
+    array.push(node.value);
+  return array;
 }
 
 function nth(list, position) {
   // Your code here
+    if (!list)
+    return undefined;
+  else if (position == 0)
+    return list.value;
+  else
+    return nth(list.rest, position - 1);
 }
 
 function prepend(element, list) {
   // Your code here
+    return {value: value, rest: list};
 }
 
 // Problem 4: Deep comparison
 function deepEqual(obj1, obj2) {
   // Your code here
+    if (obj1 === obj2) return true;
+  
+  if (obj1 == null || typeof a != "object" ||
+      obj2 == null || typeof b != "object")
+    return false;
 }
 
 
diff --git a/chapter05.js b/chapter05.js
index d1372cb..cba55a1 100644
--- a/chapter05.js
+++ b/chapter05.js
@@ -21,12 +21,37 @@ ancestry.forEach(function(person) {
 // Problem 1: Flattening
 function flatten(arrays) {
   // Your code here
+    if(!Array.isArray(arrays)){
+    return [arrays];
+  }
+  var my_array = [];
+  for (var i = 0; i<arrays.length;i++){
+    my_array =my_array.concat(flatten(arrays[i]));
+  }
+  return my_array;
 }
 
 // Problem 2: Mother-child age difference
 /* This must return the average age difference instead of printing it */
 function averageMomChildAgeDiff() {
   // Your code here
+  function average(array) {
+  function plus(a, b) { return a + b; }
+  return array.reduce(plus) / array.length;
+}
+
+var byName = {};
+ancestry.forEach(function(person) {
+  byName[person.name] = person;
+});
+
+var differences = ancestry.filter(function(person) {
+  return byName[person.mother] != null;
+}).map(function(person) {
+  return person.born - byName[person.mother].born;
+});
+
+return average(differences);
 }
 
 // Problem 3: Historical life expectancy
@@ -35,6 +60,10 @@ function averageMomChildAgeDiff() {
  */
 function averageAgeByCentury() {
   // Your code here
+    function plus(a, b) { return a + b; }
+  return array.reduce(plus) / array.length;
+}
+// still thinking
 }