5 and 12
We used to play a game when we were in College. Dunno who started it. But, the game goes like this.
One of my friends asked me to quickly tell a number between 5 and 12. I said 7. Then, he told me most people whom he asked told 7. I did not believe it and decided to try for myself. To my surprise, about 70% of the people I asked said 7 
!!!
I have wondered what could be the reason, maybe something related to psychology, numbers …
Maybe because 12 -5 = 7
or 12 + 5 = 17 (seventeen), drop the teen, we get seven !!
It’s so astonishing to see how the human brain thinks, isn’t it?
Cheers
SRK