Saturday, April 25, 2009

Not too good by half

Greg and I were in a used bookstore last week and overheard the following conversation:

Customer: How much is this book?

Proprietor: All books are half priced.

Customer: So how much is this book?

Proprietor: All books are half of the original price.

Customer (looking at the book): The original price on this book is $9.99. How much would this book be?

Proprietor: Well, the price of the book would be half of $10.

Customer: So how much would that be?

Proprietor (more than a little curtly): You take $10 and divide by two, so $5.

Customer: Oh.

I wonder how often the proprietor has that conversation. I do appreciate he tried to make it a teaching moment, with the whole "divide by two" instruction. That reminds me of a conversation a colleague had with a student this week, which went something like:

Student: How big is Mars?

Professor: It's about half the diameter of the Earth.

Student: What do you mean?

Professor: Mars is about half of the diameter of the Earth.

Student: I don't understand you.

Professor: You take the Earth's diameter and you multiply it by 0.5.

Student: Why didn't you just say so?


hagdirt said...

Considering how long it takes me to subtract a check total in the checkbook, I figure I'll be where they are any day now. It's not so much that my math skills atrophied, it's more like someone stuck gum over the padlock and now I can't get in.

I'm sorry.

Jackie M. said...