diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 000000000..b7be55eb7
Binary files /dev/null and b/.DS_Store differ
diff --git a/00_hello/hello.rb b/00_hello/hello.rb
new file mode 100644
index 000000000..52008fc13
--- /dev/null
+++ b/00_hello/hello.rb
@@ -0,0 +1,7 @@
+def hello
+	"Hello!"
+end
+
+def greet(who)
+  "Hello, #{who}!"
+end
\ No newline at end of file
diff --git a/01_temperature/temperature.rb b/01_temperature/temperature.rb
new file mode 100644
index 000000000..80cbbdb24
--- /dev/null
+++ b/01_temperature/temperature.rb
@@ -0,0 +1,7 @@
+def ftoc(temp)
+  (temp - 32) * 5.0 / 9.0
+end
+
+def ctof(temp)
+  temp * 9 / 5.0 + 32
+end
\ No newline at end of file
diff --git a/02_calculator/calculator.rb b/02_calculator/calculator.rb
new file mode 100644
index 000000000..eff4af732
--- /dev/null
+++ b/02_calculator/calculator.rb
@@ -0,0 +1,27 @@
+def add(num1, num2)
+  num1 + num2
+end
+
+def subtract(num1, num2)
+  num1 - num2
+end
+
+def sum(arr)
+  return 0 if arr.empty?
+  arr.inject(:+)
+end
+
+def multiply(arr)
+  return 0 if arr.empty?
+  arr.inject(:*)
+end
+
+def power(num1, pow)
+  num1**pow
+end
+
+def factorial(num)
+  return 0 if num == 0
+  fac = [*1..num]
+  fac.inject(:*)
+end
\ No newline at end of file
diff --git a/02_calculator/calculator_spec.rb b/02_calculator/calculator_spec.rb
index fef7e9d00..1096621ff 100644
--- a/02_calculator/calculator_spec.rb
+++ b/02_calculator/calculator_spec.rb
@@ -77,23 +77,38 @@
 # once the above tests pass,
 # write tests and code for the following:
 
-describe "#multiply" do
+describe "multiply" do
 
-  it "multiplies two numbers"
+  it "multiplies two numbers" do
+    expect(multiply([10,4])).to eq(40)
+  end
 
-  it "multiplies several numbers"
-  
+  it "multiplies several numbers" do
+    expect(multiply([10,4,2])).to eq(80)
+  end
 end
 
-describe "#power" do
-  it "raises one number to the power of another number"
+describe "power" do
+  it "raises one number to the power of another number" do
+    expect(power(10,2)).to eq(100)
+  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(0)
+  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/.DS_Store b/03_simon_says/.DS_Store
new file mode 100644
index 000000000..7c71df58d
Binary files /dev/null and b/03_simon_says/.DS_Store differ
diff --git a/03_simon_says/simon_says.rb b/03_simon_says/simon_says.rb
new file mode 100644
index 000000000..82c821a23
--- /dev/null
+++ b/03_simon_says/simon_says.rb
@@ -0,0 +1,39 @@
+def echo(word)
+  word
+end
+
+def shout(word)
+  word.upcase
+end
+
+def repeat(word, t=2)
+  result = word
+  (t-1).times do
+    result = result + " " + word
+  end
+  result
+end
+
+def start_of_word(word, num)
+  word.slice(0, num)
+end
+
+def first_word(phrase)
+  phrase.split(" ")[0]
+end
+
+def titleize(phrase)
+  result = ""
+  phrase.split(" ").each_with_index do |word, index|
+    if index == 0
+      result = result + word.capitalize + " "
+    else
+      if word == "and" || word == "the" || word == "over"
+        result = result + word + " "
+      else
+        result = result + word.capitalize + " "
+      end
+    end
+  end
+  result.strip
+end
\ No newline at end of file
diff --git a/04_pig_latin/pig_latin.rb b/04_pig_latin/pig_latin.rb
new file mode 100644
index 000000000..008135194
--- /dev/null
+++ b/04_pig_latin/pig_latin.rb
@@ -0,0 +1,19 @@
+def translate(words)
+  vowels = ["a", "e", "i", "o", "u"]
+  result = ""
+  words.split(" ").each do |word|
+    if vowels.include?(word[0])
+      result += word + "ay" + " "
+    else
+      while !vowels.include?(word[0])
+        if word.slice(0, 2) == "qu"
+          word = word.slice(2, word.length) + word.slice(0, 2)
+        else
+          word = word.slice(1, word.length) + word[0]
+        end
+      end
+      result += word + "ay" + " "
+    end
+  end
+  result.strip
+end
\ No newline at end of file
diff --git a/05_silly_blocks/silly_blocks.rb b/05_silly_blocks/silly_blocks.rb
new file mode 100644
index 000000000..66316c8f3
--- /dev/null
+++ b/05_silly_blocks/silly_blocks.rb
@@ -0,0 +1,14 @@
+def reverser
+  result = yield.split(" ").map { |word| word.reverse }
+  result.join(" ")
+end
+
+def adder(num = 1)
+  yield + num
+end
+
+def repeater(num = 1)
+  num.times do
+    yield
+  end
+end
\ No newline at end of file
diff --git a/06_performance_monitor/performance_monitor.rb b/06_performance_monitor/performance_monitor.rb
new file mode 100644
index 000000000..d933df63a
--- /dev/null
+++ b/06_performance_monitor/performance_monitor.rb
@@ -0,0 +1,6 @@
+def measure(num = 1)
+  beg_time = Time.now
+  num.times { yield }
+  finish_time = Time.now
+  (finish_time - beg_time) / num
+end
\ No newline at end of file
diff --git a/07_hello_friend/friend.rb b/07_hello_friend/friend.rb
new file mode 100644
index 000000000..1cd3936de
--- /dev/null
+++ b/07_hello_friend/friend.rb
@@ -0,0 +1,9 @@
+class Friend
+  def greeting(who = nil)
+    if who
+      "Hello, #{who}!"
+    else
+      "Hello!"
+    end
+  end
+end
\ No newline at end of file
diff --git a/08_book_titles/book.rb b/08_book_titles/book.rb
new file mode 100644
index 000000000..f26ba563a
--- /dev/null
+++ b/08_book_titles/book.rb
@@ -0,0 +1,12 @@
+class Book
+  def initialize
+    @title = ''
+    @untitlized_words = ['a', 'an', 'of', 'in', 'and', 'the', 'over']
+  end
+  def title=(value)
+    @title = value.split(' ')
+  end
+  def title
+    @title.map.with_index { |word, index| @untitlized_words.include?(word) && index > 0 ? word : word.capitalize }.join(' ')
+  end
+end
\ No newline at end of file
diff --git a/09_timer/timer.rb b/09_timer/timer.rb
new file mode 100644
index 000000000..55694112c
--- /dev/null
+++ b/09_timer/timer.rb
@@ -0,0 +1,14 @@
+class Timer
+  def initialize
+    @seconds = 0
+  end
+  def seconds
+    @seconds
+  end
+  def seconds=(value)
+    @seconds = value
+  end
+  def time_string
+    [@seconds / 3600, @seconds / 60 % 60, @seconds % 60].map { |t| t.to_s.rjust(2, '0') }.join(':')
+  end
+end
\ No newline at end of file
diff --git a/10_temperature_object/temperature.rb b/10_temperature_object/temperature.rb
new file mode 100644
index 000000000..19dbeddf8
--- /dev/null
+++ b/10_temperature_object/temperature.rb
@@ -0,0 +1,31 @@
+class Temperature
+  def initialize(options = {})
+    @f = options[:f]
+    @c = options[:c]
+  end
+  def in_fahrenheit
+    return @f if @f
+    @c * 9 / 5.0 + 32
+  end
+  def in_celsius
+    return @c if @c
+    (@f - 32) * 5 / 9.0
+  end
+  def self.from_celsius(c)
+    Temperature.new(:c => c)
+  end
+  def self.from_fahrenheit(f)
+    Temperature.new(:f => f)
+  end
+end
+
+class Celsius < Temperature
+  def initialize(t)
+    super(:c => t)
+  end
+end
+class Fahrenheit < Temperature
+  def initialize(t)
+    super(:f => t)
+  end
+end
\ No newline at end of file
diff --git a/11_dictionary/dictionary.rb b/11_dictionary/dictionary.rb
new file mode 100644
index 000000000..9ad2a5012
--- /dev/null
+++ b/11_dictionary/dictionary.rb
@@ -0,0 +1,33 @@
+class Dictionary
+  def initialize
+    @entries = {}
+  end
+  def entries
+    @entries
+  end
+  def add(entry)
+    return @entries.merge!(entry) if entry.is_a?(Hash)
+    @entries[entry] = nil
+  end
+  def keywords
+    @entries.keys.sort
+  end
+  def include?(value)
+    keywords.include?(value)
+  end
+  def find(word)
+    results = {}
+    @entries.each do |key, value|
+      results[key] = value if key.match(/#{word}/)
+    end
+    results
+  end
+  def printable
+    s = ''
+    keywords.each do |key|
+      s += "[#{key}] \"#{@entries[key]}\""
+      s += "\n" if keywords.index(key) != keywords.length - 1
+    end
+    s
+  end
+end
\ No newline at end of file
diff --git a/12_rpn_calculator/rpn_calculator.rb b/12_rpn_calculator/rpn_calculator.rb
new file mode 100644
index 000000000..a9cb1941a
--- /dev/null
+++ b/12_rpn_calculator/rpn_calculator.rb
@@ -0,0 +1,66 @@
+class RPNCalculator
+  attr_accessor :stack
+  attr_accessor :value
+  def initialize
+    @stack = []
+    @value = 0
+  end
+  def push(num)
+    @stack.push(num)
+  end
+  def operate
+    error_empty if @stack.length < 2
+    second = @stack.pop
+    first = @stack.pop
+    new_value = yield(second, first)
+    @stack.push(new_value)
+    @value = new_value
+  end
+  def plus
+    operate { |second, first| first + second }
+    @value
+  end
+  def minus
+    operate { |second, first| first - second }
+    @value
+  end
+  def divide
+    operate { |second, first| first.to_f / second.to_f }
+    @value
+  end
+  def times
+    operate { |second, first| first * second }
+    @value
+  end
+  def error_empty
+    raise "calculator is empty"
+  end
+  def tokens(string)
+    string.split(" ").map do |token|
+      if token.match(/\d/)
+        token.to_i
+      elsif ['+', '-', '*', '/'].include?(token)
+          token.to_sym
+      end
+    end
+  end
+  def evaluate(string)
+    tokens(string).each do |token|
+      if token.is_a?(Integer)
+        push(token)
+      else
+        case token
+        when :+
+          plus
+        when :-
+          minus
+        when :*
+            times
+        when :/
+            divide
+        end
+      end
+    end
+    @value
+  end
+end
\ No newline at end of file
diff --git a/14_array_extensions/array_extensions.rb b/14_array_extensions/array_extensions.rb
new file mode 100644
index 000000000..dcabcc5de
--- /dev/null
+++ b/14_array_extensions/array_extensions.rb
@@ -0,0 +1,12 @@
+class Array
+  def sum
+    return 0 if self.empty?
+    self.inject(:+)
+  end
+  def square
+    self.map { |e| e**2 }
+  end
+  def square!
+    self.map! { |e| e**2 }
+  end
+end
\ No newline at end of file
diff --git a/15_in_words/in_words.rb b/15_in_words/in_words.rb
new file mode 100644
index 000000000..94e7e45cc
--- /dev/null
+++ b/15_in_words/in_words.rb
@@ -0,0 +1,42 @@
+class Fixnum
+  def in_words
+    words_map = {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'}
+    if self == 0
+      return "zero"
+    end
+    words = ""
+    number = self
+    if number / 1_000_000_000_000 > 0
+      words += (number / 1_000_000_000_000).in_words + " trillion "
+      number %= 1_000_000_000_000
+    end
+    if number / 1_000_000_000 > 0
+      words += (number / 1_000_000_000).in_words + " billion "
+      number %= 1_000_000_000
+    end
+    if number / 1_000_000 > 0
+      words += (number / 1_000_000).in_words + " million "
+      number %= 1_000_000
+    end
+    if number / 1000 > 0
+      words += (number / 1000).in_words + " thousand "
+      number %= 1000
+    end
+    if number / 100 > 0
+      words += (number / 100).in_words + " hundred "
+      number %= 100
+    end
+    if number > 0
+      if number < 20
+        words += words_map[number]
+      else
+        words += words_map[(number.to_s[0].to_i) * 10]
+        if number % 10 > 0
+          words += " " + words_map[number%10]
+        end
+      end
+    end
+    words.strip
+  end
+end
+