10% off isn't that much ma'am

I used to work at a garden center in Lexington, Massachusetts. One of deals that we gave was a ten percent discount to all senior citizens (meaning ages 65 and older). Now perhaps math skills weren't taught in elementary schools way back then, but it still boggles my mind how many arguments I used to get into with senior citizens about this policy....

Whole Numbers Less Than 65

     "Sir, I can't give you the discount, you're only 43."
     "I'm old enough! I've paid my dues! Gimme the 10 percent."
     "Sir, come back in 22 years and I'll be glad to."

     "Er, I forgot my I.D. But I was born in 1939!"
     "Really?"
     "Oh, I mean 1929!"

Commutative Property Of Multiplication

     "OK, sir, that comes to $37.80, after tax."
     "You're supposed to take the ten percent off after you do the tax."
     "Come again?"
     "After you ring everything up, you add the tax, and THEN you take off the ten percent. You took the ten percent off BEFORE you did the tax."
     "But it comes out the same because you're taxed less."
     "Sonny, just ring it up again like I told you."

     I ring it up, again. It comes to $37.80, again.

     "No, no, damnit, you did it wrong again! Let me talk to your manager!"

10% Off Isn't That Much Ma'am

     "OK, ma'am, that comes to $6.62."
     "Oh, dear, I only have a five. I was hoping you'd give me that ten percent discount."
     "I did, ma'am."
     "You did? And it was still $6.62! Good heavens."
     "Well, ma'am, the price came to $7.00. Ten percent of that is only seventy cents."
     "Seventy cents! That's all?"
     "10% off isn't that much, ma'am."
     "Well, it's not what it used to be!"