diff --git a/chapter04.js b/chapter04.js
index 12f6ef0..eeaa304 100644
--- a/chapter04.js
+++ b/chapter04.js
@@ -6,50 +6,134 @@
  *    - DO NOT modify the number of parameters for each function.
  */
 
-
 // Problem 1: The sum of a range
 function range(start, end, step=1) {
-  // Your code here
-}
+  var array = [];
+  if (arguments.length === 3) { //if 3rd argument is entered 
+    step = arguments[2];        
+  }
+    if (start > end) {          // decrement or reverse in descending order
+    step = -1;
+  }
+  var negative = function(i, end) {
+    if (start > end || step < 0) {
+      return i >= end;          // largest number be the start  
+    } else {
+      return i <= end;
+    }
+  }
+  for (var i = start; negative(i, end); i+=step) {
+    array.push(i);
+  }
+  return array;
+
+};
 
 function sum(array) {
-  // Your code here
+  var total = 0;
+  for (var i = 0; i < array.length; i++) {
+    total += array[i];
+  }
+  return total;
+};
 }
 
+
+
+
 // Problem 2: Reversing an Array
 function reverseArray(array) {
-  // Your code here
+  var newArray = [];
+  for (var i = 0; i < array.length; i++) {
+    newArray.unshift(array[i]); // insert each element at its start
+  }  
+  return newArray;
 }
 
 function reverseArrayInPlace(array) {
-  // Your code here
+  var temp = [];
+  for (var i = 0; i < Math.floor(array.length/2);i++) { //round down and loop over half the length of the array
+    temp[i] = array[i]; //avoid overwritting
+    array[i] = array[array.length - 1 - i]; //replace first half with other back half
+    array[array.length - 1 - i] = temp[i]; //replace back half with temporary variable
+  }
+  return array;
 }
 
+
+
+
 // Problem 3: A List
-function arrayToList(array) {
-  // Your code here
+function arrayToList (array) {
+  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
+function listToArray (list) {
+  var holder = [];
+  for (var i = list; i; i = i.rest) {
+    holder.push(i.value);
+  }
+  return array;
 }
 
-function nth(list, position) {
-  // Your code here
+function nth (list, position) {
+  if list is null
+    undefined
+  else if position == 0
+    list.value
+  else
+    nth(list.rest, position - 1)
 }
 
-function prepend(element, list) {
-  // Your code here
+function prepend (element, list) {
+  list = {value: element, rest: lists}
+  return list;
 }
 
+
+
+
 // Problem 4: Deep comparison
-function deepEqual(obj1, obj2) {
-  // Your code here
-}
+var deepEqual = function (obj1, obj2) {
+  if (obj1 === obj2) { 
+    return true;
+  }  
+  else if (obj1 == null || tpropertyInYeof obj1 != "object" || obj2 == null || tpropertyInYeof y != "object")
+    return false;
+
+    var propertyInX = 0;
+    var propertyInY = 0;
+ 
+
+    for (var prop in obj1) {
+      propertyInX += 1;
+    }
+ 
+    for (var prop in obj2) {
+      propertyInY += 1;
+      if (!(prop in obj1) || !deepEqual(obj1[prop], obj2[prop])) {
+        return false;
+      }
+    }
+ 
+  return propertyInX === propertyInY;
+};
+
+
+
+
 
 
 // Do not modify below here.
+
 module.exports = {
+
   range, sum, reverseArray, reverseArrayInPlace,
+
   arrayToList, listToArray, nth, prepend, deepEqual
+
 };
diff --git a/chapter05.js b/chapter05.js
index d1372cb..b7476f4 100644
--- a/chapter05.js
+++ b/chapter05.js
@@ -20,7 +20,13 @@ ancestry.forEach(function(person) {
 
 // Problem 1: Flattening
 function flatten(arrays) {
-  // Your code here
+	var arrays = [[1, 2, 3], [4, 5], [6]];
+	console.log(arrays.reduce(function(prev, curr) {
+
+  return prev.concat(curr);
+}, ));
+
+// → [1, 2, 3, 4, 5, 6]
 }
 
 // Problem 2: Mother-child age difference
@@ -33,11 +39,37 @@ function averageMomChildAgeDiff() {
 /* This must return the object/map with centuries as keys and average age
     for the century as the value
  */
-function averageAgeByCentury() {
-  // Your code here
+function averageAgeByCentury(array) {
+  function plus(a, b) { return a + b; }
+  return array.reduce(plus) / array.length;
 }
 
+function groupBy(array, groupOf) {
+  var groups = {};
+  array.forEach(function(element) {
+    var groupName = groupOf(element);
+    if (groupName in groups)
+      groups[groupName].push(element);
+    else
+      groups[groupName] = [element];
+  });
+  return groups;
+}
+
+var byCentury = groupBy(ancestry, function(person) {
+  return Math.ceil(person.died / 100);
+});
+
+for (var century in byCentury) {
+  var ages = byCentury[century].map(function(person) {
+    return person.died - person.born;
+  });
+  console.log(century + ": " + averageAgeByCentury(ages));
+}
 
-// Do not modify below here.
-module.exports = { flatten, averageMomChildAgeDiff, averageAgeByCentury };
 
+}
+
+
+// Do not modify below here.
+module.exports = { flatten, averageMomChildAgeDiff, averageAgeByCentury };
\ No newline at end of file