diff --git a/README.md b/README.md
index 6c8e7f1..e776217 100644
--- a/README.md
+++ b/README.md
@@ -1,17 +1,17 @@
-#Math Tools
+# Math Tools
 
-##Overview
+## Overview
 This project builds some basic math functions for the calculus of series. 
 
-##How to use it
+## How to use it
 Just import the mathtools module. Each function is described in the code comments.
 
-###Functions to be implemented: 
+### Functions to be implemented: 
 * `isPrime`: tells if a number is prime.
 * `factorial`: Calculates the factorial of a number.
 * `fib`: Calculates the n value of the fibonacci sequence.
 * `geometric`: Calculates the sum of a geometric serie. 
 * `arithmetic`: Calculates the sum of an arithmetic serie.
 
-##How to test this 
-Run the test.py
\ No newline at end of file
+## How to test this 
+Run the test.py
diff --git a/mathtools.py b/mathtools.py
index 58081fa..54e6d70 100644
--- a/mathtools.py
+++ b/mathtools.py
@@ -10,3 +10,35 @@ def isPrime(n):
         if n % i == 0:
             return False
     return True
+def factorial(n):
+    '''Returns the factorial of a number'''
+    if n == 0:
+        return 1
+    else:
+        return n * factorial(n-1)
+def arithmetic(a, difference, n):
+    '''Calculates the sum of a arithmetic serie of n elements.
+       An arithmetic sequence is of the form: a, a+d, a+2d, a+3d,...
+       n is the number of elements in the sequence.'''
+    #Get the arithmetic sequence
+    sequence = [a+difference*x for x in range(n)]
+    #Calculates its sum
+    return sum(sequence)
+def fib(n):
+    ''' Calculates the n value of the fibonacci sequence'''
+    if n == 0:
+        return 0
+    elif n == 1:
+        return 1
+    else:
+        return fib(n-1)+fib(n-2)
+def geometric(a, ratio, n):
+    '''Calculates the sum of a geometric serie of n elements.
+       A geometric sequence is of the form: a, a*r, a*r*r, a*r*r*r,...
+       n is the number of elements in the sequence.'''
+    #Use the sum formula:
+    return a*(1-ratio**n)/(1-ratio)
+    #Get the geometric sequence
+    sequence = [a*(ratio**x) for x in range(n)]
+    #Calculates its sum
+    return sum(sequence)
diff --git a/test.py b/test.py
deleted file mode 100644
index ff90060..0000000
--- a/test.py
+++ /dev/null
@@ -1,62 +0,0 @@
-import mathtools
-
-def test_isPrime():
-    fails = 0
-    print "Testing isPrime"
-    primes = [2, 3, 5, 7, 983, 991, 997]
-    not_primes = [4, 6, 8, 9, 993, 994, 995, 999]
-    for prime in primes:
-        if mathtools.isPrime(prime):
-            print '+ ',  # Pass the test
-        else:
-            fails += 1
-            print '- ',
-    for not_prime in not_primes:
-        if mathtools.isPrime(not_prime):
-            fails += 1
-            print '- ',
-        else:
-            print '+ ',  # Pass the test
-
-    if not fails:
-        print "TEST OK"
-    else:
-        print ("FOUND ", fails, " ERRORS")
-
-
-def test_factorial():
-    print "Testing factorial "
-    fails = 0
-    factorials = [(5, 120), (10, 3628800), (7, 5040), (12, 479001600)]
-    for f in factorials:
-        if mathtools.factorial(f[0]) == f[1]:
-            print '+ ',  # Pass the test
-        else:
-            fails += 1
-            print '- ',
-    if not fails:
-        print "TEST OK"
-    else:
-        print "FOUND ", fails, " ERRORS"
-
-def test_fib():
-    print "Testing fib "
-    fails = 0
-    fib = [(1, 1), (0, 0), (3, 2), (4, 3), (6, 8), (7, 13), (20, 6765)]
-    for f in fib:
-        if mathtools.fib(f[0]) == f[1]:
-            print '+ ',  # Pass the test
-        else:
-            fails += 1
-            print '- ',
-    if not fails:
-        print "TEST OK"
-    else:
-        print "FOUND ", fails, " ERRORS"
-
-functions = ('isPrime', 'factorial', 'fib')
-for f in functions:
-    if hasattr(mathtools, f):
-        globals()['test_'+f]()
-    else:
-        print "*", f, "IS NOT DEFINED"
\ No newline at end of file