Finish adding beginner math challenges

Author: bgroveben

challenges/4.1.Addition/lesson_tests.py

@@ -8,5 +8,5 @@ def test_main(self):
         self.assertEqual(total, 20)
 
 # To run the tests from the console:
-# Make sure that you are in the 'addition' directory
+# Make sure that you are in the '4.1.Addition' directory
 # ⇒  python3 -m unittest lesson_tests

challenges/4.2.Subtraction/lesson.md

@@ -6,10 +6,11 @@ In Python, an integer (int) is one of 3 distinct numeric types.
 In this exercise, you will subtract two integers using the minus (-) operator.
 - https://docs.python.org/3.6/library/operator.html#operator.sub
 - https://docs.python.org/3/library/operator.html#mapping-operators-to-functions
+
 ```
 >>> 4 - 2
 2
 ```
 
 **_Instructions:_**  
-**Change the 0 so that total will equal 10.**  
+**Change the 0 so that total will equal 10.**

challenges/4.2.Subtraction/lesson_tests.py

@@ -8,5 +8,5 @@ def test_main(self):
         self.assertEqual(total, 10)
 
 # To run the tests from the console:
-# Make sure that you are in the 'subtraction' directory
+# Make sure that you are in the '4.2.Subtraction' directory
 # ⇒  python3 -m unittest lesson_tests

challenges/4.3.Multiplication/lesson.md

@@ -0,0 +1,16 @@
+## Python Multiplication
+
+Python uses the asterisk (\*) operator for multiplication.  
+If any or all of the numbers being multiplied are floating point numbers, then the product will be a float.
+- https://docs.python.org/3/library/operator.html#operator.mul
+- https://docs.python.org/3/library/operator.html#mapping-operators-to-functions
+- https://docs.python.org/3/library/stdtypes.html#numeric-types-int-float-complex
+```
+>>> 3 * 3
+9
+>>> 4.0 * 4
+16.0
+```
+
+**_Instructions:_**  
+**Change the 0 so that product will equal 80.**

challenges/4.3.Multiplication/lesson_code.py

@@ -0,0 +1,7 @@
+### Modify the code below ###
+
+product = 8 * 0
+
+### Modify the code above ###
+
+print(product)

challenges/4.3.Multiply/lesson_settings.json renamed to challenges/4.3.Multiplication/lesson_settings.json

@@ -0,0 +1,8 @@
+import unittest
+import lesson_code
+
+class MultiplicationTests(unittest.TestCase):
+    def test_main(self):
+        product = lesson_code.product
+        self.assertIsInstance(product, int)
+        self.assertEqual(product, 80)

challenges/4.3.Multiplication/lesson_tests.py

@@ -0,0 +1,18 @@
+## Python Float Division
+
+Python 3 distinguishes between integer (floor) division and float (true) division.  
+Python uses a single forward slash (/) operator for float division.  
+When using float division, even if the quotient (result) is a whole number like 1 or 2, a floating point number will be returned instead of an int.  
+- https://docs.python.org/3/library/operator.html#operator.truediv
+- https://docs.python.org/3/library/operator.html#mapping-operators-to-functions
+- https://docs.python.org/3/library/stdtypes.html#numeric-types-int-float-complex
+```
+>>> 1 / 1
+1.0
+>>> 3 / 2
+1.5
+```
+
+**_Instructions:_**  
+**When you run the existing code, the variable named quotient will have a value of 1.0**    
+**Change the the second number (the denominator) so that quotient has a value of 2.5**  

challenges/4.4.Float_Division/lesson.md

@@ -0,0 +1,7 @@
+### Modify the code below ###
+
+quotient = 5 / 5
+
+### Modify the code above ###
+
+print(quotient)