Showing Revision 3 created 05/25/2016 by Udacity Robot.

1. Title:
   2 - Travel Times SOL
2. Description:

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   Okay.
   I'm going to just jump right in and
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   hand simulate what's going on here.
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   These first three lines we just
   declare three variables and
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   set them to initial values,
   so I'm going to do that.
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   Okay, so
   that's what that would look like.
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   And then here in display,
   I'm saying display this arithmetic here.
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   Let's look and
   see what the values of day 1, day 2, and
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    day 3 are at this point in the program.
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    Day 1 is 15.
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    Day 2 is 22 and day 3 is 18.
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    Now, this might seem a little bit silly
    that I went off here to the side and
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    started keeping track
    of these variables, but
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    as the programs get more complicated and
    variables kind of change and
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    get modified in this space, it's really
    important to be keeping track of things.
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    Anyways, the key insight for
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    this problem is that you're doing
    both addition and a division here.
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    Now, if you remember from when Katherine
    was talking about order of operation,
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    division always comes before addition.
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    Meaning the first thing that's going to
    happen is this division right here.
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    So, 18 gets divided by 3, which is 6.
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    And then we have 15 plus 22 plus 6,
    which equals 43.
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    So, it's going to print out 43.
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    So, is that correct?
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    Well, what we're trying to
    do is find the average.
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    Finding the average involves
    adding up all the numbers and
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    then dividing by the number
    of numbers you have.
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    But we did the addition too early,
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    we do it before we've added
    up these three numbers.
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    Really, it should be 15 plus 22
    plus 18 then divided by three.
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    So 43 is not the correct answer.
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    And to make this code
    do the correct thing,
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    you should be surrounding these
    three variables with parentheses.
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    Then, you'll add 15 plus 22 plus 18.
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    And then divide it by 3, which will give
    you the correct answer of about 18.3.