The Casio ƒx-115MS.

Surprisingly, this is one of the best calculators I have ever owned.

I purchased it for using during my Fundamentals of Engineering exam as it was one of the few calculators that they allowed that did basic “solve for x”.

Now, 6 years later, I use it daily because: 1) I’ve never had to replace the batteries, 2) it lets you build a calculation on the screen and make changes to it.

Due to it being a ridiculously inexpensive calculator ($17 on Amazon), I’m picking up one for my office too.

My TI-92+, on the other hand, has gone into almost permanent storage because the batteries always need replaced and it does far too much for basic every-day usage. I’m actually surprised because I used my TI-92+ virtually every day of my college career.

Of course, with my current job, I don’t do anywhere near the same sort of math I did in college.