Exercise 3: Numbers And Math

Every programming language has some kind of way of doing numbers and math. Do not worry, programmers lie frequently about being math geniuses when they really aren't. If they were math geniuses, they would be doing math, not writing ads and social network games to steal people's money.

This exercise has lots of math symbols. Let's name them right away so you know what they are called. As you type this one in, say the names. When saying them feels boring you can stop saying them. Here are the names:

  • + plus
  • - minus
  • / slash
  • * asterisk
  • % percent
  • < less-than
  • > greater-than
  • <= less-than-equal
  • >= greater-than-equal

Notice how the operations are missing? After you type in the code for this exercise, go back and figure out what each of these does and complete the table. For example, + does addition.

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print "I will now count my chickens:"

print "Hens", 25 + 30 / 6
print "Roosters", 100 - 25 * 3 % 4

print "Now I will count the eggs:"

print 3 + 2 + 1 - 5 + 4 % 2 - 1 / 4 + 6

print "Is it true that 3 + 2 < 5 - 7?"

print 3 + 2 < 5 - 7

print "What is 3 + 2?", 3 + 2
print "What is 5 - 7?", 5 - 7

print "Oh, that's why it's False."

print "How about some more."

print "Is it greater?", 5 > -2
print "Is it greater or equal?", 5 >= -2
print "Is it less or equal?", 5 <= -2

What You Should See

$ python ex3.py 
I will now count my chickens:
Hens 30
Roosters 97
Now I will count the eggs:
7
Is it true that 3 + 2 < 5 - 7?
False
What is 3 + 2? 5
What is 5 - 7? -2
Oh, that's why it's False.
How about some more.
Is it greater? True
Is it greater or equal? True
Is it less or equal? False
$

Extra Credit

  1. Above each line, use the # to write a comment to yourself explaining what the line does.
  2. Remember in Exercise 0 when you started python? Start python this way again and using the above characters and what you know, use python as a calculator.
  3. Find something you need to calculate and write a new .py file that does it.
  4. Notice the math seems "wrong"? There are no fractions, only whole numbers. Find out why by researching what a "floating point" number is.
  5. Rewrite ex3.py to use floating point numbers so it's more accurate (hint: 20.0 is floating point).

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