How many even integers are there between 1 and 199

Why not make a simpler model and learn from it?

How many even integers are there between 1 and 11?  Let n=11.  Type out the even integers:  2, 4, 6, 8, 10.  So, if n=11, the number of even integers between 1 and n=11 is (11-1).2, or (10)/2, or 5.

Make another model for, say, n=21.  type out all the even integers between 1 and 21.  Does our model work?    It predicts (21-1)/2, or 10, even integers between 1 and 21.

Have fun!

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