A woman goes into a sports store to buy a rod and reel for her grandson's 21st birthday. She doesn't know which one to get, so she just grabs one and goes over to the counter. A check-out clerk is standing there wearing dark glasses.

She says, "Excuse me, sir. Can you tell me anything about this rod and reel?" He says, "Ma'am, I'm completely blind, but if you'll drop it on the counter, I can tell you everything you need to know about it from the sound it makes."

She doesn't believe him, but drops it on the counter anyway. He says, "That's an eight-foot surf caster Shakespeare graphite 667 Model rod fitted with a Shimano Calcutta 400 reel, spooled with 20lb Berkley Fireline. It's a good all around combination, and it's on sale this week for only $199.00."

She says, "It's amazing that you can tell all that just by the sound of it dropping on the counter. I'll take it!" As she opens her purse, her credit card drops on the floor. She bends down to pick it up and accidentally breaks wind. At first she is really embarrassed, but then realises it's not likely that the blind clerk could tell it was she who farted. He may not even know that she was the only person around.

The man rings up the sale and says, "That'll be $254.50 please." The woman is totally confused by this and asks, "Didn't you tell me it was on sale for $199.00? How did you get $254.50?" He replies, "Yes, Ma'am, the rod and reel is $199.00, but the duck caller is $36.00 and the fishing bait is $19.50.