diff --git a/README.md b/README.md
index a8d2878..186b863 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,19 @@
 
 more functions will be added soon
 
+#### New in version 0.0.3
+
+   1. future_given_present
+   2. present_given_future
+   3. annuity_given_present
+   4. annuity_given_future
+   5. present_given_annuity(
+   6. future_given_annuity
+
+#### Pending
+   1. include more functions
+   3. add some test units
+
 ## Installation
 
 Add this line to your application's Gemfile:
@@ -22,7 +35,6 @@ require "financial_maths"
 
 include FinancialMaths
 
-calculate = Credit.new
 ```
 
 ### Calculate Fixed payment equity
@@ -30,7 +42,7 @@ A credit in a period of 15 years, the amount is $100.000.000 and the interest is
 call the method following the next instruction.
 	
 ```ruby
-calculate.fixed_payment_equity(15,100000000,0.0144594763)
+fixed_payment_equity(15,100000000,0.0144594763)
 ```
 The result is a hash with the plan of payments, it looks like that
 	
@@ -42,6 +54,14 @@ The result is a hash with the plan of payments, it looks like that
 	.
 	]
 
+The lists of the methods and they params
+
+  future_given_present(present_value, interest, term)
+  present_given_future(future_value, interest, term)
+  annuity_given_present(present_value, interest, term)
+  annuity_given_future(future_value, interest, term)
+  present_given_annuity(annuity, interest, term)
+  future_given_annuity(annuity, interest, term)
 
 ## Contributing
 
diff --git a/lib/financial_maths.rb b/lib/financial_maths.rb
index 7056c2d..96f8a58 100644
--- a/lib/financial_maths.rb
+++ b/lib/financial_maths.rb
@@ -1,22 +1,61 @@
 require "financial_maths/version"
 
 module FinancialMaths
-  class Credit
-    def fixed_payment_equity(year, amount, year_interest)
-      years = year*12
-      monthly_payments = amount/years
-      result = []
-      result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}
-
-      for i in 1..years
-        interest = amount * year_interest
-        month_payment = monthly_payments + interest 
-        amount -= monthly_payments
-        #date += 1
-        result << {:period=> i, :payment => month_payment, :interest => interest, :monthly_payment => monthly_payments, :balance => amount}
-      end
-      result
+
+  def fixed_payment_equity(year, amount, year_interest)
+    years = year*12
+    monthly_payments = amount/years
+    result = []
+    result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}
+
+    for i in 1..years
+      interest = amount * year_interest
+      month_payment = monthly_payments + interest
+      amount -= monthly_payments
+      #date += 1
+      result << {:period=> i,
+                 :payment => month_payment,
+                 :interest => interest,
+                 :monthly_payment => monthly_payments,
+                 :balance => amount}
     end
+    result
+  end
+
+  def fixed_payment_amortization(year, amount, year_interest)
+
+  end
+
+  # hallar futuro dado el valor presente
+  def future_given_present(present_value, interest, term)
+    (present_value.to_f * (1 + interest.to_f) ** term).round(4)
+  end
+
+  # hallar presente dado el futuro
+  def present_given_future(future_value, interest, term)
+    (future_value.to_f / (1 +interest.to_f) ** term).round(4)
+  end
+
+  # hallar Anualidad dado el valor presente
+  def annuity_given_present(present_value, interest, term)
+     (present_value.to_f * ((interest *(1+interest.to_f) ** term) / ((1 + interest.to_f) ** term) -1)).round(4)
+  end
+
+  # hallar anualidad dado el valor futuro
+  def annuity_given_future(future_value, interest, term)
+     (future_value.to_f * (interest.to_f / ((1 + interest) ** term)-1)).round(4)
+  end
+
+  # hallar presente dado la anualidad
+  def present_given_annuity(annuity, interest, term)
+    (annuity.to_f * (((1 + interest.to_f) ** term) -1) / (interest.to_f * (1 + interest.to_f) ** term )).round(4)
   end
-  
+
+  # hallar futuro dado la anualidad
+  def future_given_annuity(annuity, interest, term)
+    (annuity * (((1 + interest.to_f) ** term) -1) / interest.to_f ).round(4)
+  end
+
 end
+
+
diff --git a/lib/financial_maths/version.rb b/lib/financial_maths/version.rb
index 310cb22..9a17e1b 100644
--- a/lib/financial_maths/version.rb
+++ b/lib/financial_maths/version.rb
@@ -1,3 +1,3 @@
 module FinancialMaths
-  VERSION = "0.0.1"
+  VERSION = "0.0.3"
 end