<p>Ok. I think it’s time for another advanced strategy. I call the following formula the “Fence Post Formula.”</p>
<p>Description: The number of integers from a to b, inclusive, is b-a+1. </p>
<p>For example, let’s count the number of integers from 5 to 12, inclusive. They are 5, 6, 7, 8, 9, 10, 11, 12, and we see that there are 8 of them. Now 12 – 5 = 7 which is not the correct amount, but 12 – 5 + 1 = 8 which is the correct amount.</p>
<p>If you ever happen to forget this little formula test it out on a small list of numbers as I just did. But it’s nice to have this one committed to memory so that it is there for you when you need it.</p>
<p>Note that if you put up a fence that is 10 feet long, and put up fence-posts every foot, then there are 10 – 0 + 1 = 11 fence-posts.</p>