i=0
while(i<1):
<something with i>
i=i+.1
Very frustrating, but in retrospect very eye opening.
I think that's a good lesson for kids.
That's how I learned about it years ago.
To many, a rounding error makes the answer "wrong", and suddenly the tool has switched from a reliable one into an untrustworthy one.
By middle school, kids should have learned that you can't trust calculators. There are all sorts of numbers like pi, e, sqrt(2) that are impossible to represent. Once you start getting into trig, you have to accept rounding.
Explaining _why_ .1 isn't representable requires explaining IEEE-754 and explaining _that_ requires an understanding of binary numeric representation.
I teach college students who find this confusing, so I think it's fair that the average person finds floating point behavior confusing (in fact, I've had to explain to Physics Professors doing computation simulation work why their 1-<tiny number> isn't working out the way they expect -- though they initially tried using double doubles to get around the problem).