The US Military has many smallish nuclear reactors - in every combat submarine in the fleet, for example. They're still fairly large, complicated, and expensive.

So, it's a textbook problem in your opinion. I think that you're right (and that kids shouldn't be using calculators for quite a while into math).

My daughter's math textbook is more old-fashioned, and it has find the missing addend type questions starting in 2nd grade IIRC. They use the notation of an empty box for the child to fill in.

You power plants push water? Around here we have power plants provide electricity, and pumping stations push water.

The key factor here is REPEATABLE. If it cannot be repeated it is just a meaningless statistical fluke.

Or it means that different people are affected differently, and it becomes a question of who gets into the studies.

Here's an easy way to get around 'can't use the last 6 passwords' issue:

password1 password2 password3 password4 password5 password6 password7 password1

You only have to remember what number you're on.

Of course, there are lots of permutations on this (passwordA-Z, p1assword pa1ssword, if case sensitive: Password pAssword, etc etc.)