In the how-to-get-a-pain-in-the-back department, it amazes me how shockingly naive I am about certain things at an age when I ought to know better.

Take the other day, for example. I had ordered a load of gravel for a driveway I was doing some work on and just assumed that once the load was delivered, the guy or guys who were in the truck would help me spread it out.

So a fellow pulls up in this gigantic dump truck, hops out, inspects the driveway and says, “You know what, Bo? I’m going to try and jerk this stuff out the best I can for you because — let me tell you what — raking it out is going to a real pain in the (rear end).”

“OK, great!” But meanwhile I’m thinking, how bad can it really be with two of us doing the work? Well, at any rate, he hops back in the cab; tilts the bed up until the gravel starts to pour, and then advances all herky jerky-like in order to spread it over the better part of the driveway.

But something went wrong and all of a sudden about 1½ tons of rock came cascading out like an avalanche and formed a huge mound right in the middle of the driveway. The truck kept going and started picking up speed.

The driver stuck his head out the window and said something unintelligible over the roar of the diesel engine.

“What?!” I yelled.

“I said,” he hollered back in somewhat of an exaggerated fashion, “have a nice day!”

“But, but, what a minute! I need HELP!” But it was too late. He was gone and I was stuck with the aforementioned back-breaking task, confirming once again that one never ceases to live and learn the hard way.

***

Regarding recent columns, I’m afraid I may have inadvertently been a bit misleading concerning the privileges of having a TSA Known Traveler Number while flying. Quite by accident, of course, but nonetheless not absolving me of having blown it.

The purpose of getting the Known Traveler Number is to get “pre-check” status, which is a much more convenient and hassle-free way of getting through airport security. Having a KTN helps significantly but does not guarantee pre-check status, as my wife has had the misfortune of finding out recently and as otherwise pointed out to me by Robert Watson.

“My wife and I got our KTN’s about a year ago and have flown a number of times since,” he writes. “She has always gotten ‘pre-check’ whereas I haven’t. When I asked the TSA people, they very pointedly told me that having a number is no guarantee and that there is still a random element to it.”

***

Following the column pertaining to logic and problem-solving, Jonathan Walker felt inspired to send two intriguing math exercises that demonstrate the irrefutability and mystery of their multi-layered perfection. Equally amazing is how mathematicians discover these sorts of things.

Exercise 1:

1) Pick any number.

2) Double it.

3) Then add 6.

4) Divide that figure in half.

5) Subtract the originally-picked number (from step 1) from the total from step 4.

6) Take note of the answer and then repeat the exercise starting with a different number. What do you observe?

Exercise 2:

1) Pick a three-digit number (such as 726, for example.)

2) Reverse the number (to 627.)

3) Subtract smaller number from the larger (726 - 627 = 099.)

4) Reverse the number from step 3 (099 becomes 990.)

5) Add the number from step 4 to the result from step 3.

6) Take note of the sum and then repeat the exercise starting with a different three-digit number. Notice anything?

Amazing!

Edward M. Gilbreth is a Charleston physician. Reach him at edwardgilbreth@comcast.net.