(There’s a power blackout while I am being checked out of a convenience store. My purchase is $27.15 and I have just handed the young lady at the till $40.00.)

Cashier: “I’m sorry, but the power is off and I can’t make change.”

Me: “I gave you $40, so you owe me $12.85.”

Cashier: “As if!”

Me: “Pardon me?”

Cashier: “How do you know?”

Me: “I did it in my head.”

Cashier: “Yeah, right!”

(At this point, the manager comes up and asks what the problem is.)

Cashier: “The bill is $27.15 and he gave me $40.00, but the power is out and I can’t figure the change. He tells me that it’s $12.85.”

Manager: “It is.”

Cashier: “How do you know?!”

Manager: “I did it in my head.”

Cashier: “As if!”

Manager: “Go stock the shelves…”

(The manager turns to me and shrugs apologetically.)

Manager: “She’s starting university this term in Engineering. Any bets on how long that lasts?”