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[MUSIC]

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Let's practice some basic Ruby to make
sure that everything you've learned so

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far sticks.

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We'll review numeric types such as fix,
num and float, as well as math operations.

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We're gonna ask you to build a simple Ruby
program that calculates the average of

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some numbers.

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I've attached a work space to this
video which includes an average .rb

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starter file,
with instructions as Ruby comments.

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You should open the work space now.

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If you have Ruby installed on your
computer you can choose file,

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download work space.

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And that will download
all the files to your

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computer where you can edit and run them.

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Or you can just set it and
run everything in the work space.

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Write your code in the average.rb file and
save your work.

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Then switch to the terminal and
type ruby average.rb to run your program.

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Up here at the top of the file
we've already defined four Ruby

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variables for you.

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Your job is to take the value
of all those variables and

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calculate the average,
that is the mean of them.

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You can do this by adding all
their values together and

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then dividing by the number of values,
that's four values in this case.

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Now there's a little catch to this,
for the numbers 12, 7, 5 and 10,

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you should get an average of 8.5, not 8.

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If you find that you got
the number of 8 even,

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it's probably because you divided
by a fixed sum, an integer.

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So make sure that you're
dividing by a float instead.

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See the teacher's notes for

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videos that can help you fix
this problem if it arises.

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There's an extra credit problem down
here at the bottom you can try.

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You can prompt the user for some values
to average by populating the E, B, C and

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D variables by calling the get s method.

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Note however, that the get s method
returns the string not a number.

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So you'll need to call
the to_f method on the value

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returned by gets to convert it to a float.

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That is when we type gets.to_f and
then store that value in a variable.

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Then you can calculate an average of all
the variables as you did previously.

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I've linked to some videos in
the teacher's notes which you can refer to

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if you get stuck.

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After you've written your program
you can proceed to the next video

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where you can compare
my solution to yours.

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Ready?

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Get started on your program.

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I'll show you my version and
the next video.