When I was at school, we were taught when using a calculator you should also do a mental arithmetic “first approximation” (ie. rough guess, ballpark figure) to verify the result. A useful cross-check for not being way out due to miss-keying or getting a decimal point in the wrong place.
This lunchtime I handed over a £20 note for a £2.65 sandwich in the canteen and the cash register said to give me back £14.20 change, and the lady on the till couldn’t see what the problem was when I told her that was wrong. I had to tell her that she had charged me £5.80 which was way too much.
It turned out that she had another customer’s bill still rung up on the till as he hadn’t paid yet and was waiting for his toastie to be ready.
Point is that she was so dumbed down to just doing as the till said that it never occurred to her that giving back less than £15 from a £20 note for a sandwich costing less than a fiver failed the “first approximation” test.
We see this so many times – as people become more blindly reliant on technology, so they lose the ability to think and act for themselves. I’m not against technology – far from it – but the ability to spot nonsensical output is an important one. People who can’t do that are the kind of people who obey their Sat-Nav when it directs them down a railway line, up a footpath, or over a cliff.