Back of the envelope math

Reading the email that’s going around about the evolution of math skills on Chad’s blog, I’m reminded of my neighbors on the plane from San Francisco last month.

They were a middle aged Canadian couple returning from what must have been a short visit to the Bay Area. Like everyone else on the plane, they were filling out their customs form detailing their purchases abroad. I (and everyone I know) put in a rough number which is an approximation of the true amount, based on flawed memory, optimistic perspectives on personal spending and an inordinate fondness for round numbers (it helps if the number is under the tax-free limit). This neighbor was doing things “right”, adding the cost of the two items she’d bought, not just roughly, but precisely, based on receipts she slowly dug out of her purse.

She had one receipt $154.33 (or so), and one for $19.99.

(I couldn’t help peeking because I was hoping to borrow her pen when she was done).

Color me stunned when she carefully drew up a full-blown addition, one painful digit at a time, never stopping to think about what she was doing, or about shortcuts that she could have taken (as in, add $20, take away a penny — or don’t, it really doesn’t matter!). And all that mental energy wasted on a number that no one would ever look at for more than 1 second.

I guess many people would probably invoke the same about pixel-pushing and CSS tweaking. But that’s different, I tell you!

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