- I accidentally divided by zero and my paper burst into flames.
- Isaac Newton’s birthday.
- I could only get arbitrarily close to my textbook. I couldn’t
actually reach it.

- I have the proof, but there isn’t room to write it in this margin.
- I was watching the World Series and got tied up trying to prove
that it converged.

- I have a solar powered calculator and it was cloudy.
- I locked the paper in my trunk but a four-dimensional dog got in
and ate it.

- I couldn’t figure out whether i am the square of negative one or
i is the square root of negative one.

- I took time out to snack on a doughnut and a cup of coffee. I spent the rest of the night trying to figure which one to dunk.
- I could have sworn I put the homework inside a Klein bottle, but
this morning I couldn't find it.