diff --git a/00_hello/hello.rb b/00_hello/hello.rb
new file mode 100644
index 000000000..5a5ad056e
--- /dev/null
+++ b/00_hello/hello.rb
@@ -0,0 +1,7 @@
+def hello
+  "Hello!"
+end
+
+def greet(who)
+  "Hello, #{who}!"
+end
diff --git a/01_temperature/temperature.rb b/01_temperature/temperature.rb
new file mode 100644
index 000000000..be7149d19
--- /dev/null
+++ b/01_temperature/temperature.rb
@@ -0,0 +1,7 @@
+def ftoc(temp)
+  (temp - 32) * 5.0/9
+end
+
+def ctof(temp)
+  temp * 9.0/5 + 32
+end
diff --git a/02_calculator/calculator.rb b/02_calculator/calculator.rb
new file mode 100644
index 000000000..cde7cb863
--- /dev/null
+++ b/02_calculator/calculator.rb
@@ -0,0 +1,36 @@
+def add(a, b)
+  a + b
+end
+
+def subtract(a,b)
+  a - b
+end
+
+def sum(nums)
+  return 0 if nums == []
+  sum = 0
+  nums.each do |n|
+    sum += n
+  end
+  sum
+end
+
+def multiply(*args)
+  product = 1
+  args.each do |n|
+    product *= n
+  end
+  product
+end
+
+def power(base, exp)
+  base ** exp
+end
+
+def factorial(num)
+  product = 1
+  (1..num).reverse_each do |n|
+    product *= n
+  end
+  product
+end
diff --git a/02_calculator/calculator_spec.rb b/02_calculator/calculator_spec.rb
index fef7e9d00..073ede582 100644
--- a/02_calculator/calculator_spec.rb
+++ b/02_calculator/calculator_spec.rb
@@ -79,21 +79,37 @@
 
 describe "#multiply" do
 
-  it "multiplies two numbers"
+  it "multiplies two numbers" do
+    expect(multiply(3,4)).to eq(12)
+  end
+
+  it "multiplies several numbers" do
+    expect(multiply(6,7,8)).to eq(336)
+  end
 
-  it "multiplies several numbers"
-  
 end
 
 describe "#power" do
-  it "raises one number to the power of another number"
+  it "raises one number to the power of another number" do
+    expect((power(9,2))).to eq(81)
+  end
 end
 
 # http://en.wikipedia.org/wiki/Factorial
 describe "#factorial" do
-  it "computes the factorial of 0"
-  it "computes the factorial of 1"
-  it "computes the factorial of 2"
-  it "computes the factorial of 5"
-  it "computes the factorial of 10"
+  it "computes the factorial of 0" do
+    expect(factorial(0)).to eq(1)
+  end
+  it "computes the factorial of 1" do
+    expect(factorial(1)).to eq(1)
+  end
+  it "computes the factorial of 2" do
+    expect(factorial(2)).to eq(2)
+  end
+  it "computes the factorial of 5" do
+    expect(factorial(5)).to eq(120)
+  end
+  it "computes the factorial of 10" do
+    expect(factorial(10)).to eq(3628800)
+  end
 end
diff --git a/03_simon_says/simon_says.rb b/03_simon_says/simon_says.rb
new file mode 100644
index 000000000..a9182acfe
--- /dev/null
+++ b/03_simon_says/simon_says.rb
@@ -0,0 +1,29 @@
+def echo(word)
+  word
+end
+
+def shout(word)
+  word.upcase
+end
+
+def repeat(word, num=2)
+  word += ((' ' + word) * (num - 1))
+end
+
+def start_of_word(word, num=1)
+  word[0...num]
+end
+
+def first_word(word)
+  word.split(" ")[0]
+end
+
+def titleize(words)
+  return words.capitalize unless words.include?(' ')
+  little_words = ['a', 'the', 'in', 'to',
+                  'and', 'an', 'over']
+  words = words.split(' ').each_with_index do |word, i|
+    word.capitalize! unless little_words.include?(word) && i != 0
+  end
+  words.join(' ')
+end
diff --git a/04_pig_latin/pig_latin.rb b/04_pig_latin/pig_latin.rb
new file mode 100644
index 000000000..f6e0665d4
--- /dev/null
+++ b/04_pig_latin/pig_latin.rb
@@ -0,0 +1,53 @@
+def translate(words)
+  vowels = ['a', 'e', 'i', 'o', 'u']
+  special_sequences = ['qu', 'squ']
+
+  words = words.split(' ').each do |word|
+
+    # deal with words that start with vowel
+    next if starts_with_vowel?(word, vowels)
+
+    # deal with words that start with special sequence
+    next if starts_with_special_sequence?(word, special_sequences)
+
+    # deal with words that start with consonant
+    next if starts_with_consonant(word, vowels)
+
+  end
+
+  words.join(' ')
+
+end
+
+def starts_with_consonant(word, vowels)
+  i = word.length - 1
+  vowels.each do |vowel|
+    unless word.index(vowel).nil?
+      if word.index(vowel) < i
+        i = word.index(vowel)
+      end
+    end
+  end
+  start = word.slice!(0...i)
+  word << start + 'ay'
+
+end
+
+def starts_with_vowel?(word, vowels)
+  if vowels.include?(word[0])
+    word << 'ay'
+    return true
+  end
+  false
+end
+
+def starts_with_special_sequence?(word, sequences)
+  sequences.each do |seq|
+    if word.index(seq) == 0
+      word.slice!(0...seq.length)
+      word << seq + 'ay'
+      return true
+    end
+  end
+  false
+end
diff --git a/05_silly_blocks/silly_blocks.rb b/05_silly_blocks/silly_blocks.rb
new file mode 100644
index 000000000..90fe8b5a1
--- /dev/null
+++ b/05_silly_blocks/silly_blocks.rb
@@ -0,0 +1,14 @@
+def reverser()
+  return yield.reverse if yield.split(' ').size == 1
+  yield.split(' ').each { |w| w.reverse! }.join(' ')
+end
+
+def adder(num=1)
+  yield + num
+end
+
+def repeater(repeats=1)
+  repeats.times do
+    yield
+  end
+end
diff --git a/05_silly_blocks/silly_blocks_spec.rb b/05_silly_blocks/silly_blocks_spec.rb
index c64e3ef70..38f604025 100644
--- a/05_silly_blocks/silly_blocks_spec.rb
+++ b/05_silly_blocks/silly_blocks_spec.rb
@@ -29,13 +29,13 @@
   describe "adder" do
     it "adds one to the value returned by the default block" do
       expect(adder do
-        5
+               5
       end).to eq(6)
     end
 
     it "adds 3 to the value returned by the default block" do
       expect(adder(3) do
-        5
+               5
       end).to eq(8)
     end
   end
diff --git a/06_performance_monitor/performance_monitor.rb b/06_performance_monitor/performance_monitor.rb
new file mode 100644
index 000000000..440fd2de8
--- /dev/null
+++ b/06_performance_monitor/performance_monitor.rb
@@ -0,0 +1,7 @@
+def measure(n=1)
+  elapsed_time = Time.now
+  n.times do
+    yield
+  end
+  ( Time.now - elapsed_time ) / n
+end
diff --git a/07_hello_friend/friend.rb b/07_hello_friend/friend.rb
new file mode 100644
index 000000000..30469d37e
--- /dev/null
+++ b/07_hello_friend/friend.rb
@@ -0,0 +1,7 @@
+class Friend
+
+  def greeting(friend='')
+    return "Hello!" if friend == ''
+    "Hello, #{friend}!"
+  end
+end
diff --git a/08_book_titles/book.rb b/08_book_titles/book.rb
new file mode 100644
index 000000000..8469bfd36
--- /dev/null
+++ b/08_book_titles/book.rb
@@ -0,0 +1,13 @@
+class Book
+  attr_accessor :title
+
+  def title
+    non_caps = ['and', 'in', 'of', 'the', 'a', 'an']
+    @title = @title.split(' ').each_with_index do |word, i|
+      word.capitalize! unless non_caps.include?(word) && i != 0
+      word
+    end
+    @title.join(' ')
+  end
+
+end
diff --git a/09_timer/timer.rb b/09_timer/timer.rb
new file mode 100644
index 000000000..99cda89b9
--- /dev/null
+++ b/09_timer/timer.rb
@@ -0,0 +1,22 @@
+class Timer
+  attr_accessor :seconds
+
+  def initialize(seconds=0)
+    @seconds = seconds
+  end
+
+  def time_string
+    time = @seconds
+    hours, mins, secs = 0, 0, 0
+    while time > 60
+      if time >= 60 * 60
+        hours = time / 60 / 60
+        time -= hours * 60 * 60
+      elsif time >= 60
+        mins = time / 60
+        time -= mins * 60
+      end
+    end
+    human_time = "#{sprintf '%02d', hours}:#{sprintf '%02d', mins}:#{sprintf '%02d', time}"
+  end
+end
diff --git a/10_temperature_object/temperature.rb b/10_temperature_object/temperature.rb
new file mode 100644
index 000000000..8005f25a4
--- /dev/null
+++ b/10_temperature_object/temperature.rb
@@ -0,0 +1,41 @@
+class Temperature
+
+  def initialize( options = {})
+    @options = options
+  end
+
+  def in_fahrenheit
+    return @options[:f] unless @options[:f].nil?
+    (@options[:c] * 9)/5.0 + 32
+  end
+
+  def in_celsius
+    return (@options[:f] - 32) * 5/9 if @options[:c].nil?
+    @options[:c]
+  end
+
+  def self.from_celsius(temp)
+    Temperature.new({:c => temp})
+  end
+
+  def self.in_celsius
+    @options[:c]
+  end
+
+  def self.from_fahrenheit(temp)
+    Temperature.new({:f => temp})
+  end
+
+end
+
+class Celsius < Temperature
+  def initialize(temp)
+    @options = {:c => temp}
+  end
+end
+
+class Fahrenheit < Temperature
+  def initialize(temp)
+    @options = {:f => temp}
+  end
+end
diff --git a/11_dictionary/dictionary.rb b/11_dictionary/dictionary.rb
new file mode 100644
index 000000000..aad9a0f2e
--- /dev/null
+++ b/11_dictionary/dictionary.rb
@@ -0,0 +1,38 @@
+class Dictionary
+  attr_accessor :entries
+
+  def initialize(opts = {})
+    @entries = opts
+  end
+
+  def add(entry)
+    if entry.is_a?(String)
+      @entries[entry] = nil
+    else
+      @entries.merge!(entry)
+    end
+  end
+
+  def include?(keyword)
+    keywords.include?(keyword)
+  end
+
+  def find(keyword)
+    return @entries if @entries.empty?
+    @entries.select { |word, definition| word.match(keyword)}
+  end
+
+  def printable
+    printout = ''
+    keywords.each_with_index do |key, i|
+      printout << "[#{key}] \"#{@entries[key]}\""
+      printout << "\n" if i < keywords.size-1
+    end
+    printout
+  end
+
+  def keywords
+    @entries.keys.sort
+  end
+
+end
diff --git a/12_rpn_calculator/rpn_calculator.rb b/12_rpn_calculator/rpn_calculator.rb
new file mode 100644
index 000000000..23387386b
--- /dev/null
+++ b/12_rpn_calculator/rpn_calculator.rb
@@ -0,0 +1,62 @@
+class RPNCalculator
+
+  attr_reader :nums, :value
+
+  def initialize
+    @nums = []
+    @value = 0
+  end
+
+  def push(num)
+    @nums << num
+  end
+
+  def plus
+    @value = do_maths {'+'}
+  end
+
+  def minus
+    @value = do_maths {'-'}
+  end
+
+  def divide
+    @value = do_maths{'/'}
+  end
+
+  def times
+    @value = do_maths{'*'}
+  end
+
+  def evaluate(items)
+    items = tokens(items)
+    items.each do |item|
+      push(item) if item.is_a?(Fixnum)
+      times if item == :*
+      plus if item == :+
+        minus if item == :-
+        divide if item == :/
+    end
+    value
+
+  end
+
+  def tokens(tokens)
+    operators = ['+', '-', '*', '/']
+    tokens.split(' ').collect! do |token|
+      operators.include?(token)? token.to_sym : token.to_i
+    end
+  end
+
+  def do_maths
+    begin
+      @nums[-2] += @nums[-1] if yield == '+'
+      @nums[-2] -= @nums[-1] if yield == '-'
+      @nums[-2] /= @nums[-1] * 1.0 if yield == '/'
+      @nums[-2] *= @nums[-1] if yield == '*'
+    rescue NoMethodError
+      raise "calculator is empty"
+    end
+    @nums.pop
+    @val = @nums[-1]
+  end
+end
diff --git a/14_array_extensions/array_extensions.rb b/14_array_extensions/array_extensions.rb
new file mode 100644
index 000000000..e902cce6c
--- /dev/null
+++ b/14_array_extensions/array_extensions.rb
@@ -0,0 +1,18 @@
+class Array
+
+  def sum
+    return 0 if self.empty?
+    self.inject { |prev, curr| prev + curr}
+  end
+
+  def square
+    return self if self.empty?
+    self.map { |n| n**2 }
+  end
+
+  def square!
+    return self if self.empty?
+    self.map! { |n| n**2 }
+  end
+
+end
diff --git a/15_in_words/in_words.rb b/15_in_words/in_words.rb
new file mode 100644
index 000000000..0524a2139
--- /dev/null
+++ b/15_in_words/in_words.rb
@@ -0,0 +1,67 @@
+class Fixnum
+
+  def in_dictionary(word)
+    dictionary = { 1 => 'one', 2 => 'two', 3 => 'three', 4 => 'four', 5 => 'five', 6 => 'six', 7 => 'seven', 8 => 'eight', 9 => 'nine', 10 => 'ten', 11 => 'eleven', 12 => 'twelve', 13 => 'thirteen', 14 => 'fourteen', 15 => 'fifteen', 16 => 'sixteen', 17 => 'seventeen', 18 => 'eighteen', 19 => 'nineteen', 20 => 'twenty', 30 => 'thirty', 40 => 'forty', 50 => 'fifty', 60 => 'sixty', 70 => 'seventy', 80 => 'eighty', 90 => 'ninety'}
+    dictionary[word]
+  end
+
+  def in_words
+
+    # return 0 and other numbers immediately if they are in dictionary
+    return 'zero' if self == 0
+    return in_dictionary(self) unless in_dictionary(self).nil?
+
+    words = []
+    num = self
+
+    # split num into chunks of 3 digits and store in array
+    chunks = self.to_s.reverse.scan(/.{1,3}/).reverse.map!{|n| n.reverse.to_i}
+
+    # keep track of the chunk of 1000 we're on
+    z = chunks.size
+
+    chunks.each_with_index do |n, i|
+
+      n = hundreds(words, n)
+
+      if in_dictionary(n)
+        words << in_dictionary(n)
+      elsif n > 0
+        n = tens(words, n)
+        n = ones(words, n)
+      end
+
+      if chunks[i] > 0
+        words.push('trillion') if z == 5
+        words.push('billion') if z == 4
+        words.push('million') if z == 3
+        words << 'thousand' if z == 2
+      end
+
+      z -= 1
+    end
+
+    words.join(' ')
+
+  end
+
+  def ones(list, num)
+    return num unless num >= 0
+    list << in_dictionary(num)
+    num -= num
+  end
+
+  def tens(list, num)
+    return num unless num >= 10
+    list << in_dictionary(num/10*10)
+    num = num % 10
+  end
+
+  def hundreds(list, num)
+    return num unless num >= 100
+    list << in_dictionary(num/100)
+    list << 'hundred'
+    num = num % 100
+  end
+
+end
diff --git a/15_in_words/words.rb b/15_in_words/words.rb
new file mode 100644
index 000000000..305207c2a
--- /dev/null
+++ b/15_in_words/words.rb
@@ -0,0 +1,48 @@
+class Fixnum
+
+  def in_words
+    dictionary = { 0 => 'zero', 1 => 'one', 2 => 'two', 3 => 'three', 4 => 'four', 5 => 'five', 6 => 'six', 7 => 'seven', 8 => 'eight', 9 => 'nine', 10 => 'ten', 11 => 'eleven', 12 => 'twelve', 13 => 'thirteen', 14 => 'fourteen', 15 => 'fifteen', 16 => 'sixteen', 17 => 'seventeen', 18 => 'eighteen', 19 => 'nineteen', 20 => 'twenty', 30 => 'thirty', 40 => 'forty', 50 => 'fifty', 60 => 'sixty', 70 => 'seventy', 80 => 'eighty', 90 => 'ninety'}
+
+    # return / eliminate the num in dictionary immediately if it's in above dictionary
+    return dictionary[self] unless dictionary[self].nil?
+
+    # make sure zero prints as '' from here on
+    dictionary[0] = nil
+
+    # set up list into which we'll push words
+    words = []
+
+    # convert to array of fixnum e,g, 72_658 => [7,2,6,5,8]
+    num = self
+
+
+    # iterate through each number, starting from left
+    # use i to keep track of the powers of 10
+    while num > 0
+
+      exp = num.to_s.split('').size-1
+
+      # if it's in the dictionary, put it in
+      unless dictionary[num].nil?
+        words << dictionary[num]
+        num -= num/10**exp * 10**exp
+        next
+      end
+
+      # if NOT in the dictionary
+      if exp == 2
+        words << dictionary[num/10**exp]
+      end
+
+    end
+
+
+    words.join(' ')
+  end
+
+
+end
+
+
+
+puts 1099.in_words