Ruby has a few types of numbers, but the ones we are going to focus on for the minute are integers and floating-point numbers (floats). You may recall from school that integers are whole numbers and floating-point numbers are numbers that have a decimal.
1 # integer
3.14 # float
We also have access to all the basic mathematical operations we all know and love:
2 + 7 #=> 9
5 - 3 #=> 2
8 * 8 #=> 64
12 / 3 #=> 4
2 ** 3 #=> 8 (2 to the power of 3)
10 % 3 #=> 1 (remainder of 10 divided by 3)
Pretty basic stuff, except for maybe the % (modulo). The modulo works a lot like division, but instead of returning the result, it returns the remainder. So 9 % 3 returns 0 and 11 % 3 returns 2.
Now what if you have a float that you would prefer to be an integer, or vice-versa? How do you convert between the two? What about converting to other data-types?
3.14.to_i #=> 3
9.999999.to_i #=> 9
2.to_f #=> 2.0
3.to_s #=> "3"
Note that you lose some information going from floats to integers, since it always rounds down to the nearest whole number.
Try dividing integers in IRB and see if anything seems weird to you (e.g. 7/2). Why do you think this is? Now try dividing floats and see if that matches your expectations more (e.g. 7.0/2).