COUNTING
So you say you know how to count?
You know, 1,2,3,4...
What if I were to ask you, how many numbers from 1 to 10?
Obviously 10 right?
How about if I ask you how many numbers from 8 to 17?
Is it 9?
noooo
You feverishly count on your fingers and triumphantly say 10!!!
Whats a fast way to do this?
Well there are two ways:
1) 17-8=9 9+1=10 (becuase of inclusives)
Or a slicker way:
2) 8-7=1, 17-7=10 We know 1 to 10, thats just 10!